c++ - 从 cpp 方法调用 objective-c 方法

Question

我有一个这样的 cpp 类..

class MyContactListener : public b2ContactListener
{
    int countContact;
    ///this is an objective c class...
    HelloWorld *hel;


        public:
    void EndContact(b2Contact* contact)
    {
            ///initialize objective c object
        hel=[[HelloWorld alloc] autorelease];
            ///call objective c method.........
        [hel beginContact];

    }

 };

在 cpp 类中我调用了一个 objective c 方法。objective c 方法看起来像..

-(void )beginContact
{ 
    shakeCounter++;
    [_label setString:[NSString stringWithFormat:@"%d",shakeCounter]];


}

objective c 方法被调用....并且变量 shakeCounter 也增加了......但是_label 字符串未更新...._label 已正确初始化并且如果我调用则可以正常工作objective c 类的 objective c 方法使用 self....

谁能帮忙？？？

Answer 1

在 Contact 监听器中使用 Delegate 来调用 objective-c 类的方法:

class MyContactListener : public b2ContactListener
{
    public:
    MyDelegateClass *delegate;

    void BeginContact(b2Contact* contact) { 
        [delegate beginContact:contact];
    }

    void EndContact(b2Contact* contact) { 
        [delegate endContact:contact];
    }

    void PreSolve(b2Contact* contact, const b2Manifold* oldManifold) { 
        [delegate preSolve:contact manifold:oldManifold];
    }

    void PostSolve(b2Contact* contact, const b2ContactImpulse* impulse)  {  
        [delegate postSolve:contact impulse:impulse];
    }
};

为委托(delegate)声明一个协议(protocol):

#import "Box2D.h"

@protocol B2ContactListener <NSObject>

-(void) beginContact:(b2Contact*) contact; 
-(void) endContact:(b2Contact*) contact;
-(void) preSolve:(b2Contact*) contact manifold:(const b2Manifold*) oldManifold; 
-(void) postSolve:(b2Contact*) contact impulse:(const b2ContactImpulse*) impulse; 

@end

声明实现协议(protocol)的接口(interface):

@interface MyDelegateClass: CCLayer <B2ContactListener> {
  //interface code here. 
}
@end

@implementation MyDelegateClass 

-(void) beginContact:(b2Contact*) contact {
    //implement your code here
} 
-(void) endContact:(b2Contact*) contact {
    //implement your code here
} 
-(void) preSolve:(b2Contact*) contact manifold:(const b2Manifold*) oldManifold{
    //implement your code here
}  
-(void) postSolve:(b2Contact*) contact impulse:(const b2ContactImpulse*) impulse{
    //implement your code here
} 
@end

构造委托(delegate)并在您的代码中分配它。将它设置在你的世界对象中:

MyContactListener *listener = new MyContactListener();
listener->delegate = self; 
world_->SetContactListener(listener); 

现在您的 objective-c 类将接收事件。