ios - NSInvocation/invoke 对的 addTarget 失败

Question

我将目标和操作从字典值传递给 UIButtons。这工作正常，除非我尝试传递 NSInvocation/invoke 对。

//   |self| is a member of |MyClass|, which declares selector |test|

NSDictionary *button1Data = @{ @"selectorString" : NSStringFromSelector(@selector(test)),
                               @"target" : self };

[button1 addTarget:button1Data[@"target"]
            action:NSSelectorFromString(button1Data[@"selectorString"])
  forControlEvents:UIControlEventTouchUpInside];

//  button1 executes target fine

NSInvocation *testInvocation = [NSInvocation invocationWithMethodSignature:[MyClass instanceMethodSignatureForSelector:@selector(test)]];
    testInvocation.selector = @selector(test);
    testInvocation.target = self;
    [testInvocation retainArguments];

NSDictionary *button2Data = @{ @"selectorString" : NSStringFromSelector(@selector(invoke)),
                                       @"target" : testInvocation };

[button2 addTarget:button2Data[@"target"]
            action:NSSelectorFromString(button2Data[@"selectorString"])
  forControlEvents:UIControlEventTouchUpInside];

//  button2 executes gives exceptions

button2 的异常没有寄存器转储。

我忽略了什么？

Answer 1

addTarget:action:forControlEvents: 不保留目标。您的 NSInvocation 对象是在函数内部本地创建的，当没有人对它有强引用时，它将在函数结束时被释放。然后该按钮将向已释放的实例发送消息，从而导致各种不良情况。