带有枚举的 NSInvocation？

Question

------------编辑------------

长话短说：

看来我使用 NSInvocation class 不正确（缺乏指针知识）。

使用它们的方式是这样的（有效）：

NSString *str = @"string";
UIControlState state = UIControlStateNormal;
[invocation setArgument: &str atIndex: 2];
[invocation setArgument: &state atIndex: 3];

----------------原题--------

是否可以 setArgument:atIndex: 使用枚举参数？

请参阅以下示例（不起作用）：

UIButton *btn = ...;
SEL selector = @selector(setTitle:forState:);
NSInovcation *invocation = [NSInovcation invocationWithMethodSignature: [btn methodSignatureForSelector: selector]];
[invocation setSelector: selector];
[invocation setArgument: @"Test" atIndex: 2];

//Nothing happens
UIControlState state = UIControlStateNormal;
[invocation setArgument: &state atIndex: 3];

//Runtime error (the pointer is NULL)
UIControlState *state = UIControlStateNormal;
[invocation setArgument: state atIndex: 3];

//No errors but no effect
int state2 = 0;
[invocation setArgument: &state atIndex: 3];

//Compile error (casting)
[invocation setArgument: @(UIControlStateNormal) atIndex: 3];
//Runtime EXC_BAD_ACCESS
[invocation setArgument: (void *)@(UIControlStateNormal) atIndex: 3];

...
[invocation invokeWithTarget: btn];

奇怪的是（或不是），它确实适用于 performSelector:...:

[btn performSelector: selector withObject: @"Testing" withObject:@(UIControlStateNormal)];

我不确定我是否以正确的方式使用 NSInovcation。有人想详细说明一下吗？

Answer 1

试试这个：

NSString *test = @"Test";
[invocation setArgument: &test atIndex: 2];

UIControlState state = UIControlStateNormal;
[invocation setArgument: &state atIndex: 3];