使用 Invocation 来动态调用

NSInvocation 可以方便的调用

    NSMethodSignature *signature = [target.class instanceMethodSignatureForSelector:sel];
    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];
    [invocation setArgument:&userInfo atIndex:2];
    [invocation setSelector:sel];
    BOOL result = NO;
    [invocation invokeWithTarget:self.global];
    [invocation getReturnValue:&result];