这对你们中的一些人来说一定很明显,但我找不到这样的例子:
我需要一个 boost::signals2 信号来连接作为 C++ 类成员函数或仿函数的槽回调,这样我就可以将模型回调放入 Objective-C/C++ Controller 代码中。
该回调需要存储可在 C++ 回调函数内调用的 Objective-C/C++ 方法实例的类和选择器。 (我假设没有可能实际提供 Objective-C/C++ 方法的直接回调函数地址)。我假设我需要创建一个 C++ 类/仿函数的实例来包含调用 Objective-C/C++ 方法的信息。
我也不确定我是否可以分离出 Class 和 SEL(选择器)并将它们存储在 C++ 类的实例中用于回调,而不将它们作为 void* 传递。一旦 signal() 调用 C++ 回调,我希望我可以使用 class_getInstanceMethod 和 method_getImplementation 将它们转换为可用(可调用)形式。
此外,我可能希望将至少一个具有任意结构(“EventInfo”)的参数从信号发送到插槽,这可以提供有关信号性质的信息。
有谁能为黑暗点亮光明吗?
最佳答案
我花了很长时间,但我终于弄明白了。可能有更简单的方法来做到这一点,但我发现我需要在 .mm 文件中创建一个 C++ 类,它充当 boost::signals2 信号和 Objective-C 回调函数之间的桥梁:
在 CPPToCocoaModelMessageCallbacks.h 中:
/* ------------------------------------------------------------------------
class CPPToCocoaModelMessageCallback -
--------------------------------------------------------------------------- */
class CPPToCocoaModelMessageCallback
{
public:
CPPToCocoaModelMessageCallback( PMD_Signal_Messenger<PrefEvent> *theSignalClass,
int whichPrefIdxToObserve,
id pObjCClass,
SEL pObjCMethod);
~CPPToCocoaModelMessageCallback();
void CallBackMessage(PrefEvent* pPrefEvent);
private:
id fpObjCClass;
SEL fpObjCMethod;
ls_index fWhichPrefIdxToObserve;
boost::signals2::connection fTheConnection;
}; // CPPToCocoaModelMessageCallback
在 CPPToCocoaModelMessageCallbacks.mm 中
/* ------------------------------------------------------------------------
CPPToCocoaModelMessageCallback - CONSTRUCTOR
whichPrefIdxToObserve - the preference idx to observe
Pass the id and selector of the Objective-C/C++ object & method to be
called.
--------------------------------------------------------------------------- */
CPPToCocoaModelMessageCallback::CPPToCocoaModelMessageCallback(PMD_Signal_Messenger<PrefEvent> *theSignalClass, int whichPrefIdxToObserve, id pObjCClass, SEL pObjCMethod)
: fpObjCClass (pObjCClass),
fpObjCMethod (pObjCMethod),
fWhichPrefIdxToObserve (whichPrefIdxToObserve)
{
fTheConnection = theSignalClass->ObserveSignal(&CPPToCocoaModelMessageCallback::CallBackMessage, this);
}
/* ------------------------------------------------------------------------
~CPPToCocoaModelMessageCallback - DESTRUCTOR
Pass the id and selector of the Objective-C/C++ object & method to be
called.
--------------------------------------------------------------------------- */
CPPToCocoaModelMessageCallback::~CPPToCocoaModelMessageCallback()
{
fTheConnection.disconnect();
}
/* ------------------------------------------------------------------------
CPPToCocoaModelMessageCallback::CallBackMessage -
Handles single and range-type preference change events.
--------------------------------------------------------------------------- */
void CPPToCocoaModelMessageCallback::CallBackMessage(PrefEvent* pPrefEvent)
{
// Only make the callback if this event is the preference we're observing
if (pPrefEvent->GetChangedPrefIdx() == fWhichPrefIdxToObserve) {
[fpObjCClass performSelector:fpObjCMethod];
}
}
///////////////////////////////////////////////////////////////////////////
在你的 controller.mm 中:
// set up messaging from Model. The message callback functions must be destructed in dealloc.
// I've done this in awakeFromNib but it could be elsewhere
- (void)awakeFromNib {
PMD_Signal_Messenger<MyEventKind>* theModelClass = GetMyModelClassPointer();
displayMenuPrefChangedCallBack = new CPPToCocoaModelMessageCallback(theModelClass, kAppPrefDictionaryDisplayShortDef, self, @selector(displayMenuChanged));
}
/* ------------------------------------------------------------------------
displayMenuChanged - this gets called when the model fires a signal
(via CPPToCocoaModelMessageCallback::CallBackMessage())
--------------------------------------------------------------------------- */
- (void) displayMenuChanged
{
NSLog(@"displayMenuChanged\n");
// DO SOMETHING TO RESPOND TO THE SIGNAL (in this case I'm reloading an NSWebView):
[self reloadWebViewText];
}
//////////////////////////////////////////////////////////////////////////
与信号观察者模型类结合的类:
PMD_Signal_Messenger.h:
/* ------------------------------------------------------------------------
class PMD_Signal_Messenger<MyEventKind> -
This class is designed to be multiple inherited with various
Model classes.
--------------------------------------------------------------------------- */
template <class MyEventKind>
class PMD_Signal_Messenger {
public:
PMD_Signal_Messenger() { }
~PMD_Signal_Messenger() { }
template<typename Fn, typename Obj>
boost::signals2::connection ObserveSignal(Fn callback, Obj &object) {
return fSignalObservers.connect(boost::bind(callback, object, _1));
}
protected:
boost::signals2::signal<void (MyEventKind*)> fSignalObservers; // all observers of my preference changes
private:
PMD_Signal_Messenger(const PMD_Signal_Messenger& thePMD_Signal_Messenger) { assert(false); } // prevent copy constructor
};
在您要发出模型更改信号的 .cpp MODEL 文件中:
// construct theEvent (your own struct) and fire the signal with your event structure that gets passed to CPPToCocoaModelMessageCallback::CallBackMessage()
MyEventKind theEvent(someUsefulParams);
fSignalObservers(&theEvent);
关于c++ - C++ signals2 槽回调是否可以包含 Objective-C/C++ 类/选择器(方法)信息?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16951328/