从C ++函数访问Objective-C变量 [英] Access Objective-C variable from C++ function

问题描述

我正在处理一个只需要重写的项目，但这不是一个选项。

I'm working on a project that just needs to be rewritten but that is not an option at this point.

我有一个C ++函数被调用，做各种东西。我需要它从App Delegate类中读取一个变量。

I have a C++ function that is called and does all kinds of stuff. I need it to read a variable from the App Delegate class.

例如我有：

@interface MyAppDelegate : NSObject <UIApplicationDelegate> 
{
    UIWindow *window;
    MyViewController *viewController;

 int mToleranceLevel;
}

我有一个函数需要访问mToleranceLevel：

I then have a function that needs to access the mToleranceLevel:

bool FindExtrinsics(...)
{
 float maxError = mainDelegate.mMaxError;
        ...
}

问题是， ：

@interface MyClass : UIViewController 
{
  ...
}

@properties ...

bool FindExtrinsics(...);

@end

那么如何从AppDelegate类中获取一个值。我知道如何获得当前的委托：

So how would I get a value from the AppDelegate class. I do know how to get the current delegate:

mainDelegate = (RedStripeARAppDelegate *)[[UIApplication sharedApplication] delegate];

但是如何使用这个信息来获取我的C ++函数中的值。是否有一种方法来创建一个静态变量，所以我可以调用MyAppDelegate.mToleranceValue;

But how do I use this info to get the value in my C++ function. Is there a way to make a static variable so I can call MyAppDelegate.mToleranceValue;??

推荐答案

Xcode支持 Objective-C ++ ，它允许您使用C ++代码的Objective-C调用。将C ++代码文件的扩展名从.cpp（或.cc）更改为 .mm ，您就可以从C ++代码中获取值，就像从Objective-C代码中获取值一样。

Xcode supports Objective-C++, which enables you to use Objective-C calls from C++ code. Change the extension of your C++ code file from .cpp (or .cc) to .mm and you'll be able to get the value from your C++ code just as you would from Objective-C code.

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