从视图控制器中调用C++类崩溃的是，我发现了参考我的视图控制器这样

Question

我有一个C++对象：

m_applicationEngine = (ApplicationEngine *)[(GLView *)[self.parentViewController view] m_applicationEngine]; 

在我的位置委托我叫methid在类是这样的：

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation  *)newLocation fromLocation:(CLLocation *)oldLocation { 
CLLocationCoordinate2D coordinate = [newLocation coordinate]; 

NSLog(@"Location acquired %f, %f", coordinate.latitude, coordinate.longitude); 
myLocation = new Location(coordinate.latitude, coordinate.longitude); 

m_applicationEngine->GotoLoc(myLocation); 
} 

它调用GotoLoc功能，但它崩溃第一次函数访问m_applicationEngine实例的公共成员变量。我是积极的成员已经初始化。有人有主意吗？

m_applicationEngine是在GLView：UIView的initWithFrame（）中初始化的C++对象。

m_applicationEngine = new ApplicationEngine(m_renderingEngine, self); 

这里是GotoLoc（）的代码。它第一次引用m_rotation，它是它崩溃的类的成员变量。我可以在代码的其他区域调用GotoLoc（），而不是在上面的Obj-C委托函数中。

void ApplicationEngine::GotoLoc(Location *location) { 
vec3 eye = vec3(0, 0, 1); 
vec3 end = location->loc; 

// Compute the difference between where we're looking at now vs. where we want to point 
mat4 transpose; 
MatrixTranspose(transpose, m_rotation); 
MatrixVec3Multiply(eye, eye, transpose); 

//cout << "Inverse. I was here x:" << relativeVec.x << " y:" << relativeVec.y << " z:" << relativeVec.z << endl; 

// bring vectors down to the equator to measure x angle 
vec3 relativeX = vec3(eye.x, 0, eye.z); 
// reference vector is the rotation axis for the sign to be correct 
float xAngle = signed_angle(relativeX, vec3(end.x, 0, end.z), vec3(0,-1,0)); 

mat4 rotationX; 
MatrixRotationY(rotationX, -1 * xAngle); 
MatrixMultiply(m_rotation, rotationX, m_rotation); 

// need to rotate eye vector to line up on y with new target to measure y angle 
MatrixTranspose(transpose, rotationX); 
MatrixVec3Multiply(eye, eye, transpose); 
float yAngle = signed_angle(eye, end, vec3(1,0,0)); 

cout << "Went to difference of: ANGLE x: " << RADIANS_TO_DEGREES(xAngle) << " y:" << RADIANS_TO_DEGREES(yAngle) << endl; 

mat4 rotationY; 
MatrixRotationX(rotationY, -1 * yAngle); 
MatrixMultiply(m_rotation, m_rotation, rotationY); 

}您提供给我们的信息

Answer 1

最好的猜测是m_applicationEngine其实并不是一个C++对象。你在哪里创建它？在初始化？在访问器m_applcationEngine中？

如果您想得到比这更好的答案，请向我们展示GotoLoc（）的代码以及您如何初始化C++对象。

编辑（以下新发布的代码）：

我觉得m_applicationEngine为空。你应该能够确认，在GotoLoc()的第一行中检查一下并检查this（对于C++来说是否适合？我想要相当于self）的指针。

如果你的视图是在一个nib文件中，我有一种感觉initWithCoder:被用来代替initWithFrame:这可以解释为什么你的C++对象永远不会被构造。解决这个问题的最简单方法是通过属性创建和访问它，并在首次使用时对其进行初始化。

// .h file 

@property (readonly, assign) ApplicationEngine* applicationEngine; 

// .m file 

-(ApplicationEngine*) applicationEngine 
{ 
    if (m_applicationEngine == NULL) 
    { 
     m_applicationEngine = new ApplicationEngine(m_renderingEngine, self); 
    } 
    return m_applicationEngine; 
}