We have a C++ application that utilizes some basic APIs to send raw queries to a MS SQL Server. Scattered through the various translation units in our program, we have simple 1-2 line queries as C++ strings, and every now and then you'll see more complex queries that can be over 20 lines.
I can't help but think that the larger queries, specifically the 20+ line ones, should not be embedded in C++ code as constant strings. I want to propose pulling these out into separate text files that are loaded on-demand by the C++ application, however I'm not sure if this is the best approach.
What design choices are typical for situations like this? I definitely feel there needs to be improvement, I just don't know if moving the SQL queries out into data files (text files) is the best idea.
You could make a DAL (Data Access Layer).
It would be the API that the rest of the program talks to. Then you can mess around and try anything and everything (Stored procedures, caching, etc.) without disturbing the main program.
Move them into their own files, or even into their own stored procedures. Queries embedded in the application cannot be changed without a recompile, and depending on your release procedures, that could severely impair your ability to respond to emergencies or deploy hot fixes. You could alter your app to cache the file contents, if you go down that road, and even periodically check the files for updates.
the best "design choice" - for many different reasons - is to use MSSQL stored procedures whenever/wherever possible.
I've seen code that segregates SQL queries into a common module, but I don't think there's much benefit to a common "queries module" (or a standalone text file) over having the SQL queries spelled out as string literals in the module that's calling them.
Stored procedures, on the other hand, increase modularity, enhance security, and can vastly improve performance.
IMHO...
I would leave the SQL embedded in the C++ functions that use it: it will be easier to read and understand what the code does.
If you have SQL queries scattered around your code I'd say that there is some problem with the overall structure of the classes you are using: you should have some (or even just one) 'low level' classes that handle the interaction with the database, and the rest of the code uses these classes.
I personally don't like using stored procedure: if you have to support a different database server the porting will be a pain, I never saw that much of a performance improvement and to understand what the code does you have to jump back and forth between the stored procedures and the C++.
It really depends, here are some notes:
1) If all your sql code resides in the application, then your application is pretty much self contained in terms of logic. This is good as you have done in the current application. In terms of speed, this can be a little slower as SQL will need to be parsed when when you run these queries(also depends if you used Prepared statements,etc which can speed it up).
2) The second approach is to put all SQL logic as stored procedures on the server. This is a very much preferred approach for even small SQL queries whether one line or not. You just build a DAL layer. In terms of performance this is very good, however the logic lives in two different systems, your C++ app and the SQL server. You will quite likely need to build a small utility application that can translate the stored procedures input and output to template code (be it C++ or any other) to make your life easier.
3) A mixed approach with the above two. I would not recommend this route.
You need to think about how these queries are likely to change over time, and compare it to how the related C++ code is likely to change. If the queries are relatively independent of the code, and have a higher likelihood of change, then I would either load them at runtime from separate files, or use stored procedures instead. That approach allows for changing the queries without recompiling the C++ code. On the other hand, if the queries are highly coupled to the C++ code, making a change in one likely to accompany a change in the other, I would keep the queries in the code. This approach makes a change more localized and less error prone.
So we have this huge (is 11000 lines huge?) mainmodule.cpp source file in our project and every time I have to touch it I cringe.
As this file is so central and large, it keeps accumulating more and more code and I can't think of a good way to make it actually start to shrink.
The file is used and actively changed in several (> 10) maintenance versions of our product and so it is really hard to refactor it. If I were to "simply" split it up, say for a start, into 3 files, then merging back changes from maintenance versions will become a nightmare. And also if you split up a file with such a long and rich history, tracking and checking old changes in the SCC history suddenly becomes a lot harder.
The file basically contains the "main class" (main internal work dispatching and coordination) of our program, so every time a feature is added, it also affects this file and every time it grows. :-(
What would you do in this situation? Any ideas on how to move new features to a separate source file without messing up the SCC workflow?
(Note on the tools: We use C++ with Visual Studio; We use AccuRev as SCC but I think the type of SCC doesn't really matter here; We use Araxis Merge to do actual comparison and merging of files)
Merging will not be such a big nightmare as it will be when you'll get 30000 LOC file in the future. So:
Stop adding more code to that file.
Split it.
If you can't just stop coding during refactoring process, you could leave this big file as is for a while at least without adding more code to it: since it contains one "main class" you could inherit from it and keep inherited class(es) with overloaded functions in several new small and well designed files.
Find some code in the file which is relatively stable (not changing fast, and doesn't vary much between branches) and could stand as an independent unit. Move this into its own file, and for that matter into its own class, in all branches. Because it's stable, this won't cause (many) "awkward" merges that have to be applied to a different file from the one they were originally made on, when you merge the change from one branch to another. Repeat.
Find some code in the file which basically only applies to a small number of branches, and could stand alone. Doesn't matter whether it's changing fast or not, because of the small number of branches. Move this into its own classes and files. Repeat.
So, we've got rid of the code that's the same everywhere, and the code that's specific to certain branches.
This leaves you with a nucleus of badly-managed code - it's needed everywhere, but it's different in every branch (and/or it changes constantly so that some branches are running behind others), and yet it's in a single file that you're unsuccessfully trying to merge between branches. Stop doing that. Branch the file permanently, perhaps by renaming it in each branch. It's not "main" any more, it's "main for configuration X". OK, so you lose the ability to apply the same change to multiple branches by merging, but this is in any case the core of code where merging doesn't work very well. If you're having to manually manage the merges anyway to deal with conflicts, then it's no loss to manually apply them independently on each branch.
I think you're wrong to say that the kind of SCC doesn't matter, because for example git's merging abilities are probably better than the merge tool you're using. So the core problem, "merging is difficult" occurs at different times for different SCCs. However, you're unlikely to be able to change SCCs, so the issue is probably irrelevant.
It sounds to me like you're facing a number of code smells here. First of all the main class appears to violate the open/closed principle. It also sounds like it is handling too many responsibilities. Due to this I would assume the code to be more brittle than it needs to be.
While I can understand your concerns regarding traceability following a refactoring, I would expect that this class is rather hard to maintain and enhance and that any changes you do make are likely to cause side effects. I would assume that the cost of these outweighs the cost of refactoring the class.
In any case, since the code smells will only get worse with time, at least at some point the cost of these will outweigh the cost of refactoring. From your description I would assume that you're past the tipping point.
Refactoring this should be done in small steps. If possible add automated tests to verify current behavior before refactoring anything. Then pick out small areas of isolated functionality and extract these as types in order to delegate the responsibility.
In any case, it sounds like a major project, so good luck :)
The only solution I have ever imagined to such problems follows. The actual gain by the described method is progressiveness of the evolutions. No revolutions here, otherwise you'll be in trouble very fast.
Insert a new cpp class above the original main class. For now, it would basically redirect all calls to the current main class, but aim at making the API of this new class as clear and succinct as possible.
Once this has been done, you get the possibility to add new functionalities in new classes.
As for existing functionalities, you have to progressively move them in new classes as they become stable enough. You will lose SCC help for this piece of code, but there is not much that can be done about that. Just pick the right timing.
I know this is not perfect, though I hope it can help, and the process must be adapted to your needs!
Additional information
Note that Git is an SCC that can follow pieces of code from one file to another. I have heard good things about it, so it could help while you are progressively moving your work.
Git is constructed around the notion of blobs which, if I understand correctly, represent pieces of code files. Move these pieces around in different files and Git will find them, even if you modify them. Apart from the video from Linus Torvalds mentioned in comments below, I have not been able to find something clear about this.
Confucius say: "first step to getting out of hole is to stop digging hole."
Let me guess: Ten clients with divergent feature sets and a sales manager that promotes "customization"? I've worked on products like that before. We had essentially the same problem.
You recognize that having an enormous file is trouble, but even more trouble is ten versions that you have to keep "current". That's multiple maintenance. SCC can make that easier, but it can't make it right.
Before you try to break the file into parts, you need to bring the ten branches back in sync with each other so that you can see and shape all the code at once. You can do this one branch at a time, testing both branches against the same main code file. To enforce the custom behavior, you can use #ifdef and friends, but it's better as much as possible to use ordinary if/else against defined constants. This way, your compiler will verify all types and most probably eliminate "dead" object code anyway. (You may want to turn off the warning about dead code, though.)
Once there's only one version of that file shared implicitly by all branches, then it's rather easier to begin traditional refactoring methods.
The #ifdefs are primarily better for sections where the affected code only makes sense in the context of other per-branch customizations. One may argue that these also present an opportunity for the same branch-merging scheme, but don't go hog-wild. One colossal project at a time, please.
In the short run, the file will appear to grow. This is OK. What you're doing is bringing things together that need to be together. Afterwards, you'll begin to see areas that are clearly the same regardless of version; these can be left alone or refactored at will. Other areas will clearly differ depending on the version. You have a number of options in this case. One method is to delegate the differences to per-version strategy objects. Another is to derive client versions from a common abstract class. But none of these transformations are possible as long as you have ten "tips" of development in different branches.
I don't know if this solves your problem, but what I guess you want to do is migrate the content of the file to smaller files independent of each other (summed up).
What I also get is that you have about 10 different versions of the software floating around and you need to support them all without messing things up.
First of all there is just no way that this is easy and will solve itself in a few minutes of brainstorming. The functions linked in your file are all vital to your application, and simply cutting them of and migrating them to other files won't save your problem.
I think you only have these options:
Don't migrate and stay with what you have. Possibly quit your job and start working on serious software with good design in addition. Extreme programming is not always the best solution if you are working on a long time project with enough funds to survive a crash or two.
Work out a layout of how you would love your file to look once it's split up. Create the necessary files and integrate them in your application. Rename the functions or overload them to take an additional parameter (maybe just a simple boolean?).
Once you have to work on your code, migrate the functions you need to work on to the new file and map the function calls of the old functions to the new functions.
You should still have your main-file this way, and still be able to see the changes that were made to it, once it comes to a specific function you know exactly when it was outsourced and so on.
Try to convince your co-workers with some good cake that workflow is overrated and that you need to rewrite some parts of the application in order to do serious business.
Exactly this problem is handled in one of the chapters of the book "Working Effectively with Legacy Code" (http://www.amazon.com/Working-Effectively-Legacy-Michael-Feathers/dp/0131177052).
I think you would be best off creating a set of command classes that map to the API points of the mainmodule.cpp.
Once they are in place, you will need to refactor the existing code base to access these API points via the command classes, once that's done, you are free to refactor each command's implementation into a new class structure.
Of course, with a single class of 11 KLOC the code in there is probably highly coupled and brittle, but creating individual command classes will help much more than any other proxy/facade strategy.
I don't envy the task, but as time goes on this problem will only get worse if it's not tackled.
Update
I'd suggest that the Command pattern is preferable to a Facade.
Maintaining/organizing a lot of different Command classes over a (relatively) monolithic Facade is preferable. Mapping a single Facade onto a 11 KLOC file will probably need to be broken up into a few different groups itself.
Why bother trying to figure out these facade groups? With the Command pattern you will be able to group and organise these small classes organically, so you have a lot more flexibility.
Of course, both options are better than the single 11 KLOC and growing, file.
One important advice: Do not mix refactoring and bugfixes. What you want is a Version of your program that is identical to the previous version, except that the source code is differently.
One way could be to start splitting up the least big function/part into it's own file and then either include with a header (thus turning main.cpp into a list of #includes, which sounds a code smell in itself *I'm not a C++ Guru though), but at least it's now split into files).
You could then try to switch all maintenance releases over to the "new" main.cpp or whatever your structure is. Again: No other changes or Bugfixes because tracking those is confusing as hell.
Another thing: As much as you may desire making one big pass at refactoring the whole thing in one go, you might bite off more than you can chew. Maybe just pick one or two "parts", get them into all the releases, then add some more value for your customer (after all, Refactoring does not add direct value so it is a cost that has to be justified) and then pick another one or two parts.
Obviously that requires some discipline in the team to actually use the split files and not just add new stuff to the main.cpp all the time, but again, trying to do one massive refactor may not be the best course of action.
Rofl, this reminds me of my old job. It seems that, before I joined, everything was inside one huge file (also C++). Then they've split it up (at completely random points using includes) into about three (still huge files). The quality of this software was, as you might expect, horrible. The project totaled at about 40k LOC. (containing almost no comments but LOTS of duplicate code)
In the end I did a complete rewrite of the project. I started by redoing the worst part of the project from scratch. Of course I had in mind a possible (small) interface between this new part and the rest. Then I did insert this part into the old project. I didn't refactor the old code to create the interface necessary, but just replaced it. Then I took made small steps from there, rewriting the old code.
I have to say that this took about half a year and there was no development of the old code base beside bugfixes during that time.
edit:
The size stayed at about 40k LOC but the new application contained many more features and presumably less bugs in its initial version than the 8 year old software. One reason of the rewrite was also that we needed the new features and introducing them inside the old code was nearly impossible.
The software was for an embedded system, a label printer.
Another point that I should add is that in theory the project was C++. But it wasn't OO at all, it could have been C. The new version was object oriented.
OK so for the most part rewriting API of production code is a bad idea as a start. Two things need to happen.
One, you need to actually have your team decide to do a code freeze on current production version of this file.
Two, you need to take this production version and create a branch that manages the builds using preprocessing directives to split up the big file. Splitting the compilation using JUST preprocessor directives (#ifdefs, #includes, #endifs) is easier than recoding the API. It's definitely easier for your SLAs and ongoing support.
Here you could simply cut out functions that relate to a particular subsystem within the class and put them in a file say mainloop_foostuff.cpp and include it in mainloop.cpp at the right location.
OR
A more time consuming but robust way would be to devise an internal dependencies structure with double-indirection in how things get included. This will allow you to split things up and still take care of co-dependencies. Note that this approach requires positional coding and therefore should be coupled with appropriate comments.
This approach would include components that get used based on which variant you are compiling.
The basic structure is that your mainclass.cpp will include a new file called MainClassComponents.cpp after a block of statements like the following:
#if VARIANT == 1
# define Uses_Component_1
# define Uses_Component_2
#elif VARIANT == 2
# define Uses_Component_1
# define Uses_Component_3
# define Uses_Component_6
...
#endif
#include "MainClassComponents.cpp"
The primary structure of the MainClassComponents.cpp file would be there to work out dependencies within the sub components like this:
#ifndef _MainClassComponents_cpp
#define _MainClassComponents_cpp
/* dependencies declarations */
#if defined(Activate_Component_1)
#define _REQUIRES_COMPONENT_1
#define _REQUIRES_COMPONENT_3 /* you also need component 3 for component 1 */
#endif
#if defined(Activate_Component_2)
#define _REQUIRES_COMPONENT_2
#define _REQUIRES_COMPONENT_15 /* you also need component 15 for this component */
#endif
/* later on in the header */
#ifdef _REQUIRES_COMPONENT_1
#include "component_1.cpp"
#endif
#ifdef _REQUIRES_COMPONENT_2
#include "component_2.cpp"
#endif
#ifdef _REQUIRES_COMPONENT_3
#include "component_3.cpp"
#endif
#endif /* _MainClassComponents_h */
And now for each component you create a component_xx.cpp file.
Of course i am using numbers but you should use something more logical based on your code.
Using preprocessor allows you to split things up without having to worry about API changes which is a nightmare in production.
Once you have production settled you can then actually work on redesign.
Well I understand your pain :) I've been in a few such projects as well and it's not pretty. There is no easy answer for this.
One approach that may work for you is to start adding safe guards in all functions, that is, checking arguments, pre/post-conditions in methods, then eventually adding unit tests all in order to capture the current functionality of the sources. Once you have this you are better equipped to re-factor the code because you will have asserts and errors popping up alerting you if you have forgotten something.
Sometimes though there are times when refactoring just may bring more pain than benefit. Then it may be better to just leave the original project and in a pseudo maintenance state and start from scratch and then incrementally adding the functionality from the beast.
You should not be concerned with reducing the file-size, but rather with reducing the class-size. It comes down to almost the same, but makes you look at the problem from a different angle (as #Brian Rasmussen suggests, your class seems to have to many responsibilities).
What you have is a classic example a known design antipattern called the blob. Take some time to read the article I point here, and maybe you may find something useful. Besides, if this project is as big as it looks, you should consider some design to prevent growing into code that you can't control.
This isn't an answer to the big problem, but a theoretical solution to a specific piece of it:
Figure out where you want to split the big file into subfiles. Put comments in some special format at each of those points.
Write a fairly trivial script that will break the file apart into subfiles at those points. (Perhaps the special comments have embedded filenames that the script can use as instructions for how to split it.) It should preserve the comments as part of the splitting.
Run the script. Delete the original file.
When you need to merge from a branch, first recreate the big file by concatenating the pieces back together, do the merge, and then re-split it.
Also, if you want to preserve the SCC file history, I expect the best way to do that is to tell your source control system that the individual piece files are copies of the original. Then it will preserve the history of the sections that were kept in that file, although of course it will also record that large parts were "deleted".
One way to split it without too much danger would be to take a historic look at all the line changes. Are there certain functions that are more stable than others? Hot spots of change if you will.
If a line hasn't been changed in a few years you can probably move it to another file without too much worry. I'd take a look at the source annotated with the last revision that touched a given line and see if there are any functions you could pull out.
Wow, sounds great. I think explaining to your boss, that you need a lot of time to refactor the beast is worth a try. If he doesn't agree, quitting is an option.
Anyway, what I suggest is basically throwing out all the implementation and regrouping it into new modules, let's call those "global services". The "main module" would only forward to those services and ANY new code you write will use them instead of the "main module". This should be feasible in a reasonable amount of time (because it's mostly copy and paste), you don't break existing code and you can do it one maintenance version at a time. And if you still have any time left, you can spend it refactoring all old depending modules to also use the global services.
Do not ever touch this file and the code again!
Treat is like something you are stuck with. Start writing adapters for the functionality encoded there.
Write new code in different units and talk only to adapters which encapsulate the functionality of the monster.
... if only one of the above is not possible, quit the job and get you a new one.
My sympathies - in my previous job I encountered a similar situation with a file that was several times larger than the one you have to deal with. Solution was:
Write code to exhaustively test the function in the program in question. Sounds like you won't already have this in hand...
Identify some code that can be abstracted out into a helper/utilities class. Need not be big, just something that is not truly part of your 'main' class.
Refactor the code identified in 2. into a separate class.
Rerun your tests to ensure nothing got broken.
When you have time, goto 2. and repeat as required to make the code manageable.
The classes you build in step 3. iterations will likely grow to absorb more code that is appropriate to their newly-clear function.
I could also add:
0: buy Michael Feathers' book on working with legacy code
Unfortunately this type of work is all too common, but my experience is that there is great value in being able to make working but horrid code incrementally less horrid while keeping it working.
Consider ways to rewrite the entire application in a more sensible way. Maybe rewrite a small section of it as a prototype to see if your idea is feasible.
If you've identified a workable solution, refactor the application accordingly.
If all attempts to produce a more rational architecture fail, then at least you know the solution is probably in redefining the program's functionality.
My 0.05 eurocents:
Re-design the whole mess, split it into subsystems taking into account the technical and business requirements (=many parallel maintenance tracks with potentially different codebase for each, there is obviously a need for high modifiability, etc.).
When splitting into subsystems, analyze the places which have most changed and separate those from the unchanging parts. This should show you the trouble-spots. Separate the most changing parts to their own modules (e.g. dll) in such a way that the module API can be kept intact and you don't need to break BC all the time. This way you can deploy different versions of the module for different maintenance branches, if needed, while having the core unchanged.
The redesign will likely need to be a separate project, trying to do it to a moving target will not work.
As for the source code history, my opinion: forget it for the new code. But keep the history somewhere so you can check it, if needed. I bet you won't need it that much after the beginning.
You most likely need to get management buy-in for this project. You can argue perhaps with faster development time, less bugs, easier maintaining and less overall chaos. Something along the lines of "Proactively enable the future-proofness and maintenance viability of our critical software assets" :)
This is how I'd start to tackle the problem at least.
Start by adding comments to it. With reference to where functions are called and if you can move things around. This can get things moving. You really need to assess how brittle the code base it. Then move common bits of functionality together. Small changes at a time.
Another book you may find interesting/helpful is Refactoring.
Something I find useful to do (and I'm doing it now although not at the scale you face), is to extract methods as classes (method object refactoring). The methods that differ across your different versions will become different classes which can be injected into a common base to provide the different behaviour you need.
I found this sentence to be the most interesting part of your post:
> The file is used and actively changed in several (> 10) maintenance versions of our product and so it is really hard to refactor it
First, I would recommend that you use a source control system for developing these 10 + maintenance versions that supports branching.
Second, I would create ten branches (one for each of your maintenance versions).
I can feel you cringing already! But either your source control isn't working for your situation because of a lack of features, or it's not being used correctly.
Now to the branch you work on - refactor it as you see fit, safe in the knowledge that you'll not upset the other nine branches of your product.
I would be a bit concerned that you have so much in your main() function.
In any projects I write, I would use main() only perform initialization of core objects - like a simulation or application object - these classes is where the real work should go on.
I would also initialize an application logging object in main for use globally throughout the program.
Finally, in main I also add leak detection code in preprocessor blocks that ensure it's only enabled in DEBUG builds. This is all I would add to main(). Main() should be short!
You say that
> The file basically contains the "main class" (main internal work dispatching and coordination) of our program
It sounds like these two tasks could be split into two separate objects - a co-ordinator and a work dispatcher.
When you split these up, you may mess up your "SCC workflow", but it sounds like adhering stringently to your SCC workflow is causing software maintenance problems. Ditch it, now and don't look back, because as soon as you fix it, you'll begin to sleep easy.
If you're not able to make the decision, fight tooth and nail with your manager for it - your application needs to be refactored - and badly by the sounds of it! Don't take no for an answer!
As you've described it, the main issue is diffing pre-split vs post-split, merging in bug fixes etc.. Tool around it. It won't take that long to hardcode a script in Perl, Ruby, etc. to rip out most of the noise from diffing pre-split against a concatenation of post-split. Do whatever's easiest in terms of handling noise:
remove certain lines pre/during concatenation (e.g. include guards)
remove other stuff from the diff output if necessary
You could even make it so whenever there's a checkin, the concatenation runs and you've got something prepared to diff against the single-file versions.
"The file basically contains the "main class" (main internal work dispatching and coordination) of our program, so every time a feature is added, it also affects this file and every time it grows."
If that big SWITCH (which I think there is) becomes the main maintenance problem, you could refactor it to use dictionary and the Command pattern and remove all switch logic from the existing code to the loader, which populates that map, i.e.:
// declaration
std::map<ID, ICommand*> dispatchTable;
...
// populating using some loader
dispatchTable[id] = concreteCommand;
...
// using
dispatchTable[id]->Execute();
I think the easiest way to track the history of source when splitting a file would be something like this:
Make copies of the original source code, using whatever history-preserving copy commands your SCM system provides. You'll probably need to submit at this point, but there's no need yet to tell your build system about the new files, so that should be ok.
Delete code from these copies. That should not break the history for the lines you keep.
I think what I would do in this situation is bit the bullet and:
Figure out how I wanted to split the file up (based on the current development version)
Put an administrative lock on the file ("Nobody touch mainmodule.cpp after 5pm Friday!!!"
Spend your long weekend applying that change to the >10 maintenance versions (from oldest to newest), up to and including the current version.
Delete mainmodule.cpp from all supported versions of the software. It's a new Age - there is no more mainmodule.cpp.
Convince Management that you shouldn't be supporting more than one maintenance version of the software (at least without a big $$$ support contract). If each of your customers have their own unique version.... yeeeeeshhhh. I'd be adding compiler directives rather than trying to maintain 10+ forks.
Tracking old changes to the file is simply solved by your first check-in comment saying something like "split from mainmodule.cpp". If you need to go back to something recent, most people will remember the change, if it's 2 year from now, the comment will tell them where to look. Of course, how valuable will it be to go back more than 2 years to look at who changed the code and why?
I have this general problem in design, refactoring or "triage":
I have an existing multi-threaded C++ application which searches for data using a number of plugin libraries. With the current search interface, a given plugin receives a search string and a pointer to a QList object. Running on a different thread, the plugin goes out and searches various data sources (locally and on the web) and adds the objects of interest to the list. When the plugin returns, the main program, still on the separate thread, adds this data to the local data store (with further processing), guarding this insertion point using a mutex. Thus each plugin can return data asynchronously.
The QT-base plugin library is based on message passing. There are a fair number of plugins which are already written and tested for the application and they work fairly well.
I would like to write some more plugins and leverage the existing application.
The problem is that the new plugins will need more information from the application. They will to need intermittent access to the local data store itself as they search. So to get this, they would need direct or indirect access both the hash array storing the data and the mutex which guards multiple access to the store. I assume the access would be encapsulated by adding an extra method in a "catalog" object.
I can see three ways to write these new plugins.
When loading a plugin, pass them
a pointer to my "catalog" at the
start. This becomes an extra,
"invisible" interface for the new
plugins. This seems quick, easy,
completely wrong according to OO but
I can't see what the future problems would be.
Add a method/message to the
existing interface so I have a
second function which could be
called for the new plugin libraries,
the message would pass a pointer to
the catalog to the plugins. This
would be easy for the plugins but it
would complicate my main code and
seems generally bad.
Redesign the plugin interface.
This seems "best" according to OO,
could have other added benefits but
would require all sorts of
rewriting.
So, my questions are
A. Can anyone tell me the concrete dangers of option 1?
B. Is there a known pattern that fits this kind of problem?
Edit1:
A typical function for calling the plugin routines looks like:
elsewhere(spec){
QList<CatItem> results;
plugins->getResult(spec, &results);
use_list(results);
}
...
void PluginHandler::getResults(QString* spec, QList<CatItem>* results)
{
if (id->count() == 0) return;
foreach(PluginInfo info, plugins) {
if (info.loaded)
info.obj->msg(MSG_GET_RESULTS, (void*) spec, (void*) results);
}
}
It's a repeated through-out the code. I'd rather extend it than break it.
Why is it "completely wrong according to OO"? If your plugin needs access to that object, and it doesn't violate any abstraction you want to preserve, it is the correct solution.
To me it seems like you blew your abstractions the moment you decided that your plugin needs access to the list itself. You just blew up your entire application's architecture. Are you sure you need access to the actual list itself? Why? What do you need from it? Can that information be provided in a more sensible way? One which doesn't 1) increase contention over a shared resource (and increase the risk of subtle multithreading bugs like race conditions and deadlocks), and 2) doesn't undermine the architecture of the rest of the app (which specifically preserves a separation between the list and its clients, to allow asynchronicity)
If you think it's bad OO, then it is because of what you're fundamentally trying to do (violate the basic architecture of your application), not how you're doing it.
Well, option 1 is option 3, in the end. You are redesigning your plugin API to receive extra data from the main app.
It's a simple redesign that, as long as the 'catalog' is well implemented and hide every implementation detail of your hash and mutex backing store, is not bad, and can serve the purpose well enough IMO.
Now if the catalog leaks implementation details then you would better use messages to query the store, receiving responses with the needed data.
Sorry, I just re-read your question 3 times and I think my answer may have been too simple.
Is your "Catalog" an independent object? If not, you could wrap it as it's own object. The Catalog should be completely safe (including threadsafe)--or better yet immutable.
With this done, it would be perfectly valid OO to pass your catalog to the new plugins. If you are worried about passing them through many layers, you can create a factory for the catalog.
Sorry if I'm still misunderstanding something, but I don't see anything wrong with this approach. If your catalog is an object outside your control, however, such as a database object or collection then you really HAVE to encapsulate it in something you can control with a nice, clean interface.
If your Catalog is used by many pieces across your program, you might look at a factory (which, at it's simplest degrades to a Singleton). Using a factory you should be able to summon your Catalog with a Catalog.getType("Clothes"); or whatever. That way you are giving out the same object to everyone who wants one without passing it around.
(this is very similar to a singleton, by the way, but coding it as a factory reminds you that there will almost certainly be more than one--also remember to allow a Catalog.setType("Clothes", ...); for testing.
We have a medium sized ColdFusion code base for our Intranet and Website. For most of the history of the code we have used hard coded links in the cfm's for where to go and for what 'save' code to tun.
In the last few years we've began using cfc's to handle more of the "navigational" code as well as more automated save code (implicitly calling the save process for a given cfc on init)
Assuming that it makes sense to begin using a framework, is it better to begin using it for newer projects or attempt a full scale conversion?
EDIT
To avoid confusion, I'm sensing that by moving to more cfc based code we are going down the path of accidentally creating our own framework. It seems to me that taking a proactive step toward using a proper framework and allowing the cfc's to process data is probably a wiser choice.
I'd only put the effort into a conversion if you were spending more than 10-20% of your time maintaining the project. (Your threshold my be lower or higher.) Other than that, use it just for new projects.
Why? I think the conversion is going to be painful, laborious and potentially a waste of valuable time.
"Assuming that it makes sense to begin
using a framework, is it better to
begin using it for newer projects or
attempt a full scale conversion?"
I would say that the biggest criteria for whether you should move to a framework are:
Am I spending a good amount of time maintaining current code, and is it difficult?
Am I repeating a lot of code? Do you find yourself writing a lot of the same thing over and over when adding to the current project?
Depending on how large the application is, it might be worth it to convert a current application to a framework if it saves you more time down the road by making maintenance easier and reducing code repetition for future additions to the current project. If you rarely maintenance the application except for a few tweaks here and there, then I would say leave it alone and use a framework only for new applications.
Frameworks have a short term cost and a long term gain.
When we start out without one we usually start building one over time indirectly to increase re-use of code, and make things more structured..
I have been a big fan of Fusebox, probably because I've just used it for so long.
What I have done in the past is, if I know the site will never be updated in into any real website functions, I just roll my own cfswitch to navigate between actions. each action I simply break down into the dsp act qry type files fusebox likes.
If ever I need to put it into fusebox, most of my circuits and actions are already done. The path forward is a bit easier.
On the other hand, if I know the client may want more in the future, I will just put it in a framework and leave it at that.
On a sidenote, I have also been checking out the very impressive ColdBox -- which seems to have some fantastic support, scalability and very well documented is cfc intensive... check them out too..
Have you considered using a framework such as fusebox instead of rolling your own? If you begin using a framework on new projects you might then find it easier to apply what you've learnt to existing projects.
I feel the need to refactor my old CF5 based code into CFC's. We already have some code in ColdSpring and Transfer but feel a large rewrite to ColdSpring and Transfer is pointless.
What tips, approaches and gotchas will I hit.
How can I make this easy?
I don't mind keeping ColdSpring in the mix but Transfer is the bit I'm scared of with the size of the project.
edit: my code base has been going for 7-8 years and is vast. To describe it would be difficult, however I'm looking for generic suggestions on approaches
Changing the whole code base just for the sake of it if it basically works would be introducing a lot of potential bugs into your system. I don’t think there is an easy way to do it.
If you look at the areas of your site which are 1: most likely to change and 2: executed the most you may be able to target some areas which could benefit from change and see how easily they would fit into a CFC based framework, and what benefits. But for most of the code if it is working OK, there may be no pressing need to change.
However whenever you need to do a major alteration to part of the system it may be worth looking at that from an OO perspective and moving the existing code over, where applicable.
In one of my ongoing projects (almost same situation, even more -- most of code is really bad) I am using technique I'd called "wave-style". General ideas I use are following:
Splitting processing from output. I can not implement true MVC here, but at least I can move view into separate templates (sometimes re-use them) and prepare all data in basic (model) templates.
Move all repeating code into components -- this is one of most important tips.
Group related functions into components. Say, all customer-related info grouped into CustomerManager.cfc, invoices into InvoiceManager.cfc etc.
Why "wave"? In a big project I can't just sit and rewrite all customer-related code. So I have make it step by step. For example, I have to work on customer signup, extend it with few attributes. I've created basic component, moved there methods to validate form (check login, email etc.) and add customer - so this page works in new style. Lated I will need to improve invoice page, where I need to get invoice owner details: I just add method into customer manager and get rid of direct queries. Later edit customer page... Also it can be called "on demand refactoring" or smth.
There can be additional stuff relying on your current project state. But it helped me a lot. Hope you'll find these tips useful.
Before you change anything: create a full set of regression tests!
When refactoring, the goal has to be preserve functionality first, so that you don't directly affect your clients.
I agree with Sergii's wave-style refactoring also - this allows you to break things into manageable chunks rather than doing everything in one go.
But whatever method you have, the more regression tests you can create, the better - it's really the only way you can confirm you haven't unintentionally changed something.
This is extremely hard (bordering on impossible) to answer without knowing any of your code.
The question is a bit like "I want to disassemble my old Volkswagen and build a new one from the parts, what should I consider?" :-)
My advice would be to start off by encapsulating your business logic into CFCs instead of worrying about the whole presentation layer of your site.
By just concentrating on the business logic, you'll be able to get the most important functionality into CFCs and ease the maintenance nightmare. It also won't be too hard to just "drop-in" these CFCs into your existing site.
After getting as much business logic into the CFCs as you can, you'll notice that the enormous monster has been cut down to size. At that point you can now decide on what you want to do with the presentation layer of your site. You're now free to pick from a multitude of frameworks available to use (CFWheels, FuseBox, ColdBox, Mode-Glue) to port over the presentation layer.
Or you could just say "the heck with it" and rewrite the whole thing in CFWheels from the start :)
If you are not using version control get that set up before you do anything else. Being able to back out of broken refactoring is a serious life saver. After that I agree with what has been posted. You will want to take on small chunks at a time - divide and conquer.