I have a set of 30 variables that I need to be able to modify and use from within any of the 50 projects in my solution. Since, the variables happen to relate to the same entity, I would like to encapsulate them in a class. I plan to have only a single instance of the class. But I would like this instance to be accessible and modifiable from any of my 50 projects in the solution. Please tell me how.
You can create a static library project and use that to make your class.
As you build other apps (console projects i would guess) under project properties for the app, you should be able to add a reference to the library project. That gets you your link.
There would also need to be a way for the app to get to your class header file.
One way to do it would be to put the path in the include.
#include "c:\somesolution\common_library\common_class.hpp"
Another way to do it, would be to add the path to the library to your VC++ Directories for the app project.
Design the solution as a shared file. Then for a bit better performance you can map the file into shared memory.
Related
I have a solution called book_example with one project inside called first_project. I want to make several more example projects called second_project, third_project etc. within this solution.
So, when I open book_example in the solution explorer it would show all of my projects. I want them to share source code so all file paths etc. should be the same.
When I right click the solution Add -> New Project even if I use a template that is exactly the same as my existing first_project all of the paths do not work. Basic things like my source.cpp say "This file does not exist or has been moved".
Edit: To be more clear, when I try a solution like the one proposed by madocter below, I get errors with the project. I.e.:
What is the correct way to create several projects within one solution that share code?
I was storing my classes in static libraries.For example modify the original header file like adding line pragma comment(lib,"MyClass") then copy files to the visual studio's include and lib folder.Whatever everything was fine until i wanted to add Menu to my class.Lib files does not have resources so i am going to use dynamic link library for this class.Is this logical that storing classes in dlls? also i dont know how to use dlls like that...
is there some examples for this? Also there is classes like CFileDialog that have resources(dialog) this kind of classes use static libraries or dynamic ?
To me, this sounds like "the wrong place to split things". In other words, if your library needs a resource that is part of the application, then it's probably not meant to be a library in the first place - it is either a proper standalone DLL that contains its own resource, because it has a complete and standalone functionality, or it's actually part of the main executable, and uses the main executable's resource.
The point of making something into a library is that it allows the separation of the library contents from the main application.
Another option is of course that you pass in the relevant resource information from the main application to your class in the library [this works for a a DLL too, of course].
My point here is that a menu is something that belongs to the main application - it knows what it has under File, Edit, View, etc. If you are writing a word processor, you may have things like "Spell checking" in there, but you don't want "Spell checking" in the Photo Editor software, but you probably want some way to get colour profile information to match the monitor's colour balance with the official colours. So your "class" to handle menus probably shouldn't "know" what the menus are, but just how to deal with menus in general - what menus you have comes from the actual main application.
I know this isn't really a direct answer to your questions...
The property manager allows having different property sets for different configurations - for example, release and debug.
However, it still means you have to manually assign each property file to each configuration.
Is there some method to automatically assign a property set to a project based on some parameters (like configuration or platform)
a specific example:
I have a solution with many sub-projects.
this projects depend on various external libraries.
for each external library I have a .props file with the relevant directories and other parameters (include , lib, dll's...)
In some cases the directory names can be easily constructed using the default macros such as $(Configuration), $(Platform), etc.
However some libraries come with a less standard \ consistent naming convention.
for these cases I create .props file which are specific to a configuration (Debug\Release) - but it requires assigning the manfully to each project, which is tedious and error prone.
This is possible, at least in principle, see this post, for example. However, I did not find a practical way to use the whole power of MSBuild in combination with c++ projects from within the IDE. Whatever smart MSBuild expressions you write down in your property sheet, once you fire up the property manager dialog in the IDE everything gets overwritten with either defaults or the values inferred from there. This is an odd behaviour and completely different from other project types. Looks like they just wanted to keep the old pre-MSBuild style of editing VCProjects...
You can record a macro and use VBA to create/generate these with a button click.
I'm working on a static library project for a c++ course I'm taking. The teacher insists that we define only one function per source file, grouping files/functions belonging to the same class in subdirectories for each class. This results in a structure like:
MyClass
\MyClass.cc (constructor)
\functionForMyClass.cc
\anotherFunctionForMyClass.cc
OtherClass
\OtherClass.cc (constructor)
Whether this is good practice or not is something I'd not like to discuss, since I'm simply obliged to organize my project in this manner.
I'm working in visual studio 2008, and somehow got strange link errors when using an identically named function (and thus filename) in two classes. This appears to be caused by the fact that visual studio puts all .obj files (one for each source file) in one intermediate directory, overwriting earlier generated object files when compiling identically named source files.
This could be solved by putting the object files in subdirectories based on the relative path of the input file. Visual studio allows one to configure the names of object files it generates and has macros to use in there, but there appears to be no macro for 'relative path of input file'.
So, is there some way to get this to work? If not, is using one project for each class the best work-around?
You are right, by default all object files are put into the same directory and their filenames are based on the source file name. The only solution I can think of is to change conflicting file's output file path in here:
Project Properties-C/C++-Output Files-Object File Name http://img37.imageshack.us/img37/3695/outputfile.png
PS. It sounds like the lecturer has a crappy (probably written by the lecturer himself) automatic code verifier that imposes this restriction. To get extra marks, offer to rewrite the parser so it works with normal/sane/non-weird projet layout.
Real answer:
Change
C/C++ => Output Files => Output File Name
to
$(IntDir)/%(RelativeDir)/
Every .obj file is going to be created in a sub folder so its not going to overwrite the previous on linking.
I can't think of any way to fudge the project settings to get VStudio to automatically split out the intermediate files into separate folders.
You have a few chances -
Build the class name into each file name. Most IDE's display just the file name in the tab view so if you do have several methods in different classes with the same name, its going to be difficult to tell them apart if the file name does not include the class name along with the method name. Which is really why I think your teachers advice is madness. I have not seen any programming style guide advocating that approach. Additionally it goes directly against the way various tools work - if you use Visual Studio to create a class, it creates one cpp file and one header, and automatically appends each new function to the single cpp file.
You could create a static library per class. When linking in static libs the obj files are all packaged up inside the .lib so conflicts are no longer a problem.
Switch comp-sci courses to one thats not being taught by a nut job. Seriously, this guy is completely out of touch with industry best practices and is trying to impose their own weird ideas on their students: Ideas that are going to have to be unlearnt the moment they leave the teaching environment.
You can also change output file name per file in its properties. Just make sure you use different names.
Can you use the class name in the filename to disambiguate? I'm thinking that you might have
MyClass
\MyClass.cc (constructor)
\function1_MyClass.cc
\function2_MyClass.cc
That would mean that every file would have a unique-enough name to defeat the problem. Is that an acceptable strategy?
You could probably arrange the properties of the project to put the object files into a folder which is below the folder of each source file. Once the project has this property, then every source file should inherit this property. (But if you've done experiments like Igor has suggested, then you may need to go through the properties as reset them back to the parent).
Having looked at the help files, I think you should go to project properties/C C++/Outpuf Files/Object File Name: and enter $(InputDir) (no trailing backslash). Every source file should then inherit this property and your .obj files should be separated.
You may need to do a Clean Solution before you make any changes.
Renaming the object files will work, but it's going to be a pain, and it will slow your compile/link cycle down. I've never figured out why, but it seems to confuse Visual Studio if the object files don't have the default names.
You could prefix the funciton name with the class name; e.g. myclass-ctor.cc, myclass-function1.cc etc.
You could have one .cc file per class which #includes the individual function files. In this case you'll need to prevent the #included files from being compiled seperately (either rename their extension or set Properties->Exclude From Build to 'Yes').
Out of curiosity, where does your teacher want you to put free functions e.g. local helper functions that might normally belong in an anonymous namespace?
If not, is using one project for each class the best work-around?
Not a good idea - apart from the fact that you won't end up with a single static library (without even more jiggery pokery), your link times are likely to increase and it will hide a
lot of pertinent info from the optimizer.
On another note; If the course is actually about C++ not OO programming, do what you need to pass but take your teacher's advice with a pinch of salt.
You don't have to put them in different translation units... why not put each function in a .h and include them all in one .cc per class? That will very likely give better output from the compiler.
I'd be asking why the teacher is insisting on this odd structure, too, the reasoning behind it should be explained. I know you didn't ask that of us, so that's all I'll say.
In Visual Studio 2010, I set
Properties -> C/C++ -> Output Files -> Output File Name
to
V:\%(Directory)$(PlatformName)_$(ConfigurationName)_%(Filename).obj
for OBJ files to end up next to the sources assuming the project lies on drive V (no idea whether there is a macro for it, yet).
By the way: $(InputDir) refers to the solution/project directory and will cause the same problem in another directory.
Say I have ini/json to store configuration setting of my desktop application,Will it be ok to have a static object with all property loaded at startup/when ever it is required or is there any other better alternative?
Since this is the very first time I am doing this ,so just wanted to know whether static object is fine or singleton pattern or something else would be better
I usually use Boost.Program_options, and I usually use a singleton.
Either way is fine.
If it was me, I would have it on construction of the config object.
cConfig Config("config.ini");
This Config class would load the settings found in the file. Any code can access the settings by doing
Config.Get("NumberOfFoobars")
For testability purposes, if there is no file in the construction, the class' settings is set to default or a log file is created with a line advising the user of the missing settings.
And then for functions that needs the config, I would pass the Config instance as part of the parameters:
DoStuff(Config, [...]);
and have DoStuff get the variables from the Config class.
This makes the class testable (you can mock Config class), readeable (at a glance, you can tell which function requires Configs) and you don't have to rely on static instances (singletons are dangerous if you don't know how to use them).
You might be interested to learn more about this
If the config settings is going to be modified by the user to determine the way the application is going to run, then it might be better to keep it in some ini file. Some users like to edit ini files directly rather than do it through the GUI. It is better to give both the options.
Also some user have multiple ini files and rotate among them for settings they need at that point of time.
Loading all your settings at startup (or the first time a setting is needed) will work most of the time, but the user will have to restart the application in order for any edits to the config file to take effect. For most users this will never be an issue, but for advanced users who like to edit config files directly this could be frustrating. On UNIX based OSs it is possible to handle the SIGHUP signal which has become a accepted trigger to re-read configuration files. There is no similar method that I know of for Windows. An alternative approach would be to keep track of the modification time of the config file to determine if the settings should be re-read.