I'm using the program Maya to make a rather large project in python. I have numerous options that will be determined by a GUI and input by the user.
One example of an option is what dimensions to render at. However I did not make a GUI yet and am still in the testing faze.
What I ultimately want is a way to have variables be able to be looked up and used by various classes/methods within multiple modules. And also that there be a way that I can test all the code without having an actual GUI.
Should I directly pass all data to each method? My issue with this is if method foo relies on variable A, but method bar needs to call foo, it could get real annoying passing these variables to Foo from everywhere its called.
Another way I saw was passing all variables through to each class instance itself and using instance variables to access. But what if an option changes, then i'd have to put reload imports every time it runs.
For testing what I use now is a module that gets variables from a config file with the variables, and i import that module and use the instance variables throughout the script.
def __init__(self):
# Get and assign all instance variables.
options = config_section_map('Attrs', '%s\\ui_options.ini' %(data_path))
for k, v in options.items():
if v.lower() == 'none':
options[k] = None
self.check_all = int(options['check_all'])
self.control_group = options['control_group']
Does anyone have advice or can point me in the right direction dealing with getting/using ui variables?
If the options list is not overly long and won't change, you can simply set member variables in the class initializer, which makes the initialization easy for readers to understand:
class OptionData(object):
def __init___(self):
#set the options on startup
self.initial_path = "//network"
self.initial_name = "filename"
self.use_hdr = True
# ... etc
If you expect the initializations to change often you can split out the initial values into the constructor for the class:
class OptionData(object):
def __init___(self, path = "//network", name = "filename", hdr=True)
self.initial_path = path
self.initial_name = name
self.use_hdr = hdr
If you need to persist the data, you can fill out the class reading the cfg file as you're doing, or store it in some other way. Persisting makes things harder because you can't guarantee that the user won't open two Maya's at the same time, potentially changing the saved data in unpredictable ways. You can store per-file copies of the data using Maya's fileInfo.
In both of these cases I'd make the actual GUI take the data object (the OptionData or whatever you call yours) as an initializer. That way you can read and write the data from the GUI. Then have the actual functional code read the OptionData:
def perform_render(optiondata):
#.... etc
That way you can run a batch process without the gui at all and the functional code will be none the wiser. The GUI's only job is to be a custom editor for the data object and then to pass it on to the final function in a valid state.
Related
Let me elaborate on the title:
I want to implement a system that would allow me to enable/disable/modify the general behavior of my program. Here are some examples:
I could switch off and on logging
I could change if my graphing program should use floating or pixel coordinates
I could change if my calculations should be based upon some method or some other method
I could enable/disable certain aspects like maybe a extension api
I could enable/disable some basic integrated profiler (if I had one)
These are some made-up examples.
Now I want to know what the most common solution for this sort of thing is.
I could imagine this working with some sort of singelton class that gets instanced globally or in some other globally available object. Another thing that would be possible would be just constexpr or other variables floating around in a namespace, again globally.
However doing something like that, globally, feels like bad practise.
second part of the question
This might sound like I cant decide what I want, but I want a way to modify all these switches/flags or whatever they are actually called in a single location, without tying any of my classes to it. I don't know if this is possible however.
Why don't I want to do that? Well I like to make my classes somewhat reusable and I don't like tying classes together, unless its required by the DRY principle and or inheritance. I basically couldn't get rid of the flags without modifying the possible hundreds of classes that used them.
What I have tried in the past
Having it all as compiler defines. This worked reasonably well, however I didnt like that I couldnt make it so if the flag file was gone there were some sort of default settings that would make the classes themselves still operational and changeable (through these default values)
Having it as a class and instancing it globally (system class). Worked ok, however I didnt like instancing anything globally. Also same problem as above
Instancing the system class locally and passing it to the classes on construction. This was kinda cool, since I could make multiple instruction sets. However at the same time that kinda ruined the point since it would lead to things that needed to have one flag set the same to have them set differently and therefore failing to properly work together. Also passing it on every construction was a pain.
A static class. This one worked ok for the longest time, however there is still the problem when there are missing dependencies.
Summary
Basically I am looking for a way to have a single "place" where I can mess with some values (bools, floats etc.) and that will change the behaviour of all classes using them for whatever, where said values either overwrite default values or get replaced by default values if said "place" isnt defined.
If a Singleton class does not work for you , maybe using a DI container may fit in your third approach? It may help with the construction and make the code more testable.
There are some DI frameworks for c++, like https://github.com/google/fruit/wiki or https://github.com/boost-experimental/di which you can use.
If you decide to use switch/flags, pay attention for "cyclometric complexity".
If you do not change the skeleton of your algorithm but only his behaviour according to the objets in parameter, have a look at "template design pattern". This method allow you to define a generic algorithm and specify particular step for a particular situation.
Here's an approach I found useful; I don't know if it's what you're looking for, but maybe it will give you some ideas.
First, I created a BehaviorFlags.h file that declares the following function:
// Returns true iff the given feature/behavior flag was specified for us to use
bool IsBehaviorFlagEnabled(const char * flagName);
The idea being that any code in any of your classes could call this function to find out if a particular behavior should be enabled or not. For example, you might put this code at the top of your ExtensionsAPI.cpp file:
#include "BehaviorFlags.h"
static const enableExtensionAPI = IsBehaviorFlagEnabled("enable_extensions_api");
[...]
void DoTheExtensionsAPIStuff()
{
if (enableExtensionsAPI == false) return;
[... otherwise do the extensions API stuff ...]
}
Note that the IsBehaviorFlagEnabled() call is only executed once at program startup, for best run-time efficiency; but you also have the option of calling IsBehaviorFlagEnabled() on every call to DoTheExtensionsAPIStuff(), if run-time efficiency is less important that being able to change your program's behavior without having to restart your program.
As far as how the IsBehaviorFlagEnabled() function itself is implemented, it looks something like this (simplified version for demonstration purposes):
bool IsBehaviorFlagEnabled(const char * fileName)
{
// Note: a real implementation would find the user's home directory
// using the proper API and not just rely on ~ to expand to the home-dir path
std::string filePath = "~/MyProgram_Settings/";
filePath += fileName;
FILE * fpIn = fopen(filePath.c_str(), "r"); // i.e. does the file exist?
bool ret = (fpIn != NULL);
fclose(fpIn);
return ret;
}
The idea being that if you want to change your program's behavior, you can do so by creating a file (or folder) in the ~/MyProgram_Settings directory with the appropriate name. E.g. if you want to enable your Extensions API, you could just do a
touch ~/MyProgram_Settings/enable_extensions_api
... and then re-start your program, and now IsBehaviorFlagEnabled("enable_extensions_api") returns true and so your Extensions API is enabled.
The benefits I see of doing it this way (as opposed to parsing a .ini file at startup or something like that) are:
There's no need to modify any "central header file" or "registry file" every time you add a new behavior-flag.
You don't have to put a ParseINIFile() function at the top of main() in order for your flags-functionality to work correctly.
You don't have to use a text editor or memorize a .ini syntax to change the program's behavior
In a pinch (e.g. no shell access) you can create/remove settings simply using the "New Folder" and "Delete" functionality of the desktop's window manager.
The settings are persistent across runs of the program (i.e. no need to specify the same command line arguments every time)
The settings are persistent across reboots of the computer
The flags can be easily modified by a script (via e.g. touch ~/MyProgram_Settings/blah or rm -f ~/MyProgram_Settings/blah) -- much easier than getting a shell script to correctly modify a .ini file
If you have code in multiple different .cpp files that needs to be controlled by the same flag-file, you can just call IsBehaviorFlagEnabled("that_file") from each of them; no need to have every call site refer to the same global boolean variable if you don't want them to.
Extra credit: If you're using a bug-tracker and therefore have bug/feature ticket numbers assigned to various issues, you can creep the elegance a little bit further by also adding a class like this one:
/** This class encapsulates a feature that can be selectively disabled/enabled by putting an
* "enable_behavior_xxxx" or "disable_behavior_xxxx" file into the ~/MyProgram_Settings folder.
*/
class ConditionalBehavior
{
public:
/** Constructor.
* #param bugNumber Bug-Tracker ID number associated with this bug/feature.
* #param defaultState If true, this beheavior will be enabled by default (i.e. if no corresponding
* file exists in ~/MyProgram_Settings). If false, it will be disabled by default.
* #param switchAtVersion If specified, this feature's default-enabled state will be inverted if
* GetMyProgramVersion() returns any version number greater than this.
*/
ConditionalBehavior(int bugNumber, bool defaultState, int switchAtVersion = -1)
{
if ((switchAtVersion >= 0)&&(GetMyProgramVersion() >= switchAtVersion)) _enabled = !_enabled;
std::string fn = defaultState ? "disable" : "enable";
fn += "_behavior_";
fn += to_string(bugNumber);
if ((IsBehaviorFlagEnabled(fn))
||(IsBehaviorFlagEnabled("enable_everything")))
{
_enabled = !_enabled;
printf("Note: %s Behavior #%i\n", _enabled?"Enabling":"Disabling", bugNumber);
}
}
/** Returns true iff this feature should be enabled. */
bool IsEnabled() const {return _enabled;}
private:
bool _enabled;
};
Then, in your ExtensionsAPI.cpp file, you might have something like this:
// Extensions API feature is tracker #4321; disabled by default for now
// but you can try it out via "touch ~/MyProgram_Settings/enable_feature_4321"
static const ConditionalBehavior _feature4321(4321, false);
// Also tracker #4222 is now enabled-by-default, but you can disable
// it manually via "touch ~/MyProgram_Settings/disable_feature_4222"
static const ConditionalBehavior _feature4222(4222, true);
[...]
void DoTheExtensionsAPIStuff()
{
if (_feature4321.IsEnabled() == false) return;
[... otherwise do the extensions API stuff ...]
}
... or if you know that you are planning to make your Extensions API enabled-by-default starting with version 4500 of your program, you can set it so that Extensions API will be enabled-by-default only if GetMyProgramVersion() returns 4500 or greater:
static ConditionalBehavior _feature4321(4321, false, 4500);
[...]
... also, if you wanted to get more elaborate, the API could be extended so that IsBehaviorFlagEnabled() can optionally return a string to the caller containing the contents of the file it found (if any), so that you could do shell commands like:
echo "opengl" > ~/MyProgram_Settings/graphics_renderer
... to tell your program to use OpenGL for its 3D graphics, or etc:
// In Renderer.cpp
std::string rendererType;
if (IsDebugFlagEnabled("graphics_renderer", &rendererType))
{
printf("The user wants me to use [%s] for rendering 3D graphics!\n", rendererType.c_str());
}
else printf("The user didn't specify what renderer to use.\n");
So this is how my program flows. User loads a file, through the menu and loadFile function will be called.
def loadFile():
dictList = defaultdict(list)
filename = askopenfilename(filetypes=[("text files","*.txt")])
#process the file content and store in dictList
return dictList
Now in the GUI, when user clicks on the load file menu, load file will get called. Since loadfile returns me a dictList object, which I need it for further processing later. How do I get the returned object without using global variables? I'm not coding in object-oriented way either.
fileMenu.add_command(label="Load File", command=loadFile)
You can't do it without using a global variable. The variable has to be stored in a way that it can be accessed from multiple functions. Since you're not using objects, your only1 choice is to use a global variable.
1 technically speaking, it's not your only choice. You could use a database of some sort, or write the value to disk, but it's the only practical choice in this scenario.
I am using this module hierarchy :
Node: {udpApp[0]<->udp<->networkLayer->wlan[0]} and wlan[0]: {CNPCBeacon<->mac<->radio}
I have given some initial parameter in the ini file for udpApp as :
**.host*.numUdpApps = 2
**.host*.udpApp[0].typename = "UDPBasicApp"
**.host*.udpApp[0].chooseDestAddrMode = "perBurst"
**.host*.udpApp[0].destAddresses = "gw1"
**.host*.udpApp[0].startTime = 1.32s
**.host*.udpApp[0].stopTime = 1.48s
But at run time I want to change the startTime and stopTime for udpAPP[0] through CNPCBeacon module. Hence I changed CNPCBeacon.cc as:-
cModule* parentmod = getParentModule();
cModule* grantParentmod = parentmod->getParentModule();
cModule* udpmod;
for (cSubModIterator iter(*grantParentmod); !iter.end(); iter++)
{
//EV<<"get the modulde "<< iter()->getFullName()<<endl;
if (strcmp(iter()->getFullName(), "udpApp[0]") == 0)
{
udpmod = iter();
break;
}
}
cPar& startTime = udpmod->par("startTime");
cPar& stopTime = udpmod->par("stopTime");
And I am successfully able to receive the values of startTime and stopTime. However I want to change these value in current module, which is resulting in an error by following code:
udpmod->par("startTime").setDoubleValue(4.2);
Can anybody please suggest me a way to change it at run time.
Declaring your parameter as volatile should solve your problem. But for future reference I'll provide further explanation below
Volatile vs. non-volatile:
Here it depends how you want to use this parameter. Mainly via the .ini file you have two types of parameters: volatile and non-volatile.
volatile parameters are read every time during your run. That woule be helpful if you want this parameter to be generated by a built-in function, for example, uniform(0,10) each time this volatile parameter will get a different value.
On the other hand non-volatile parameters are read just one, as they don't change from run to run.
Using the volatile type parameter does not give you full flexibility, in the sense that your parameter value will always fall with in a range predefined in the .ini
Dynamic Variable (parameter) Reassignment:
Instead what you could do is use a more robust approach, and re-define the variable which stores the value from that module parameter each time you have to do so.
For example in your case you could do the following:
varHoldingStartTime = par("startTime").doubleValue();
varHoldingStartTime = 4.2;
This way the actual value will change internally without reflecting to your run.
Parameter Studies:
Alternatively if you want this change of the parameter to be applied to multiple runs you could use the advanced built-in approach provided by OMNeT++ which allows you to perform Parameter Studies.
I have explained here how Parameter Studies work: https://stackoverflow.com/a/30572095/4786271 and also here how it can be achieved with constraints etc: https://stackoverflow.com/a/29622426/4786271
If none of the approaches suggested by me fit your case, answers to this question altogether might solve your problem: How to change configuration of network during simulation in OMNeT++?
EDIT: extending the answer to roughly explain handleParameterChange()
I have not used handleParameterChange() before as well, but from what can I see this function provides a watchdog functionality to the module which utilizes it.
To activate this functionality first the void handleParameterChange(const char *parameterName); has to be re-defined.
In essence what it seems to do is the following:
Assume we have two modules moduleA and moduleB and moduleB has parameter parB. moduleA changes the parB and when that happens, moduleB reacts to this change based on the behaviour defined in:
moduleB::handleParameterChange(parB);
The behaviour could be re-reading the original value for parB from the .ini etc.
I use Lua for my game engine logic. My main game loop is not done in Lua. Only special nodes in my scene hierarchy have Lua scripts attached. These scripts are executed every frame. The problem I face is that I need to keep global variable values from one frame to another.
My temporary solution looks like this:
finish = useBool("finish", false)
timer = useInt("timer", 0)
showTimer = useBool("showTimer", true)
startTimer = useInt("startTimer", 0)
play0 = useBool("play0", false)
play1 = useBool("play1", false)
play2 = useBool("play2", false)
play3 = useBool("play3", false)
delta = useInt("delta", 0)
gameOverTime = useInt("gameOverTime", 5000)
finishTime = useInt("finishTime", 5000)
checkPoint = useInt("checkPoint", 255)
<...> Game logic <...>
setInt("message", message);
setInt("checkPoint", checkPoint)
setInt("finishTime", finishTime)
setInt("gameOverTime", gameOverTime)
setInt("timer", timer)
setBool("play3", play3)
setBool("play2", play2)
setBool("play1", play1)
setBool("play0", play0)
setInt("startTimer", startTimer)
setBool("showTimer", showTimer)
setInt("timer", timer)
setBool("finish", finish);
I call special methods that retrieve global variables from hash maps in C++ at the beginning and I set them again at the end of the script.
Is there a way to do this implicitly?
Is it a bad design to use Lua not as the main game loop?
Well, while there is nothing technically wrong with your solution, you might start to notice some performance issues if you end up with a lot of global variables (something you should, in general, avoid).
With that said, there is room for improvement. For example:
At the beginning of the script, check if your global variable is nil. If it is, then you can initialize it, if not, this is probably not the first time you're running the script, so leave it unmodified. But that means a lot of pesky if-else statements, which one can easily forget about. We can do better!
I would recommend looking at Chapter 14: The Environment, from the Programming in Lua book. Here's a quick quote from the intro:
Lua keeps all its global variables in a regular table, called the environment. ... The other (actually the main) advantage is that we can manipulate this table as any other table. To facilitate such manipulations, Lua stores the environment itself in a global variable _G. (Yes, _G._G is equal to _G.)
Since _G is a table, it also has a metatable, so you can define __index and __newindex metamethods to handle access to and creation of global variables. You can find examples of this in section 14.2. Go read the whole chapter, it's not that long (if you're unfamiliar with metamethods and metatables, also look through chapter 13 - this is where Lua really shines in terms of flexibility).
Now that we've covered the trivial and normal methods, let's look at the overkill end of the spectrum. As an example I'll look at Unity's approach to scripting. A Unity javascript usually defines variables, functions, and types. Any variables defined outside of the scope of methods or types are persisted between frames because the script itself is not executed every frame. Instead, they let the script define functions and call the functions at the appropriate time. So if you want something executed every frame - you put it in the Update function. Every script can define it's own Update function because it has it's own scope. So every frame the scripting engine goes through all objects, checks if the script's scope has an Update method and calls it.
Back to Lua - a solution like this would involve creating separate environments for each object/script/whatever your node is. Then, instead of executing the script attached to your node every frame, your main loop will go through all the nodes and run a function inside of their environment. You can also switch environments, so you can set the global environment to your node's env before executing it, and then switch back when you're done. This allows your scripts to use globals as they see fit, have them persisted between frames and excludes the possibility of name collisions or global namespace pollution. Additionally you can use metamethods to nest the node's environment inside the actual global environment or inside an API environment with helper methods (basically, if __index does not find something it looks it up in a parent).
I have an existing app with a command-line interface that I'm adding a GUI to. One situation that often comes up is that I have a list of objects that inherit from one class, and need to be displayed in a list, but each subclass has a slightly different way of being displayed.
Not wanting to have giant switch statements everywhere using reflection/RTTI to do the displaying, each class knows how to return its own summary string which then gets displayed in the list:
int position = 0;
for (vector<DisplayableObject>::const_iterator iDisp = listToDisplay.begin(); iDisp != listToDisplay.end(); ++iDisp)
cout << ++position << ". " << iDisp->GetSummary();
Similar functions are there to display different information in different contexts. This was all fine and good until we needed to add a GUI. A string is no longer sufficient - I need to create graphical controls.
I don't want to have to modify every single class to be able to display it in a GUI - especially since there is at least one more GUI platform we will want to move this to.
Is there some kind of technique I can use to separate this GUI code out of the data objects without resorting to RTTI and switch statements? It would be nice to be able to take out the GetSummary functions as well.
Ideally I'd be able to have a heierarchy of display classes that could take a data class and display it based on the runtime type instead of the compile time type:
shared_ptr<Displayer> displayer = new ConsoleDisplayer();
// or new GUIDisplayer()
for (vector<DisplayableObject>::const_iterator iDisp = listToDisplay.begin(); iDisp != listToDisplay.end(); ++iDisp)
displayer->Display(*iDisp);
I don't think this will solve your problem of not needing to write the code, but you should be able to abstract the GUI logic from the data objects.
Look at a Visitor pattern (http://en.wikipedia.org/wiki/Visitor_pattern) it will allow you to add code to an existing object without changing the object itself. You can also change the visitor based on the platform.