xcode 如何从“发送者”对象访问用户定义的运行时属性？
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How to access User Defined Runtime Attribute from the 'sender' object?
提问by eric
I have a UIButtonin a Storyboard scene. The button has a User-Defined-RunTime-Attribute 'type'(String) configured. When pressed the button calls
我有一个UIButton故事板场景。该按钮配置了 User-Defined-RunTime-Attribute 'type'(String)。当按下按钮调用
-(IBAction)pressedButton:(id)sender
-(IBAction)pressedButton:(id)sender
Will I be able to access the User-Defined-RunTime-Attribute from 'sender'?
我能否从“发送者”访问用户定义的运行时属性？
回答by trojanfoe
Yes:
是的：
-(IBAction)pressedButton:(id)sender
{
id value = [sender valueForKey:key];
}
Note that you cannot use a User Defined Run Time attribute, unless you subclass UIButton and add it as a strong property, for example
请注意，您不能使用用户定义的运行时属性，除非您继承 UIButton 并将其添加为强属性，例如
@interface UINamedButton : UIButton
@property (strong) NSString *keyName;
@end
If you set a User Defined Run Time attribute, and you have not done this, Xcode will badly crash unfortunately.
如果你设置了一个用户定义的运行时间属性，而你没有这样做，不幸的是 Xcode 会严重崩溃。
You can then get that value like
然后你可以得到这个值
-(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")] )
}
