Objective-C编译错误：'SEL'之前的预期表达式

Question

在实现某些like例如

时，我遇到了奇怪的编译问题

作品：

  [self performSelector:NSSelectorFromString(member)];

不工作：

  SEL method=NSSelectorFromString(member);
  [self performSelector:method];

编译器哭泣：

methods.m:31: error: expected expression before ‘SEL’
methods.m:32: error: ‘method’ undeclared (first use in this function)
methods.m:32: error: (Each undeclared identifier is reported only once
methods.m:32: error: for each function it appears in.)

完整的方法：

 - (void)printArgs:(NSString *)member
{   
   //int val=[self compareIt:member];
    switch ([self compareIt:member])
    {
        case 1:
            //dynamically call method
            SEL method;
            method = NSSelectorFromString(member);
            NSLog(@"\n%@ is a object Member , with value: %i\n", member, [self performSelector:method]);            
            break;
        default:
            NSLog(@"\nWrong option :%@ \n", member);
    } 

}
@end

请指出正确的方向。（请注意我是Objective-C的新手）

Answer 1

它实际上是一个C问题而不是Objective-C问题。它不喜欢在case内定义变量而不限制其范围。

这应该有效：

case 1: {
    //dynamically call method
    SEL method;
    method = NSSelectorFromString(member);
    NSLog(@"\n%@ is a object Member , with value: %i\n", member, [self performSelector:method]);
}
break;