performSelector的返回值： [英] Return value for performSelector:

问题描述

performSelector的返回值是什么：如果我传递一个返回基本类型（对象）的选择器，例如NSDateComponents上的'week'（将返回一个int）？

What will the return value for performSelector: if I pass a selector that returns a primitive type (on object), such as 'week' on NSDateComponents (which will return an int)?

推荐答案

使用NSInvocation返回浮点数的示例：

An example of using NSInvocation to return a float:

SEL selector = NSSelectorFromString(@"someSelector");
if ([someInstance respondsToSelector:selector]) {
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:
                                [[someInstance class] instanceMethodSignatureForSelector:selector]];
    [invocation setSelector:selector];
    [invocation setTarget:someInstance];
    [invocation invoke];
    float returnValue;
    [invocation getReturnValue:&returnValue];
    NSLog(@"Returned %f", returnValue);
}

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