如何从'发件人'对象访问用户定义的运行时属性？

Question

我在故事板场景中有一个UIButton。该按钮具有配置的User-Defined-RunTime-Attribute'type'（String）。当按下按钮呼叫

-(IBAction)pressedButton:(id)sender

我将能够访问由“发送方”用户自定义运行时属性？

Answer 1

是：除非你继承的UIButton并将其添加为一个强大的属性你不能使用用户定义的运行时间属性，，例如

-(IBAction)pressedButton:(id)sender 
{ 
    id value = [sender valueForKey:key]; 
} 

---

注

@interface UINamedButton : UIButton 
@property (strong) NSString *keyName; 
@end 

如果您设置了“用户定义的运行时间”属性，而您还没有这样做，那么Xcode将不幸地崩溃。

然后，您可以得到像

-(IBAction)clicked:(UIControl *)sender 
    { 
    NSString *test = @"???"; 

    if ([sender respondsToSelector:@selector(keyName)]) 
      test = [sender valueForKey:@"keyName"]; 

    NSLog(@"the value of keyName is ... %@", test); 

    // if you FORGOT TO SET the keyName value in storyboard, that will be NULL 
    // if it's NOT a UINamedButton button, you'll get the "???" 

    // and for example... 
    [self performSegueWithIdentifier:@"idUber" sender:sender]; 
    // ...the prepareForSegue could then use that value in the button. 

    // note that a useful alternative to 
    // if ([sender respondsToSelector:@selector(stringTag)]) 
    // is... 
    // if ([sender respondsToSelector:NSSelectorFromString(@"stringTag")]) 
    } 

该值