子类化UIButton但不能访问我的属性 [英] Subclassing UIButton but can't access my properties

问题描述

我创建了一个UIButton的子类：

  // 
 // DetailButton.h 
 #import< Foundation / Foundation.h> 
 #import< MapKit / MapKit.h> 
 
 @interface MyDetailButton：UIButton {
 NSObject * annotation; 
} 
 
 @property（nonatomic，retain）NSObject * annotation; 
 
 
 @end 
 
 // 
 // DetailButton.m 
 // 
 
 $ b b #importMyDetailButton.h
 
 
 @implementation MyDetailButton 
 
 
 @synthesize注释; 
 
 @end 
  

我想我可以创建这个对象并设置注释对象通过执行以下操作：

  MyDetailButton * rightButton = [MyDetailButton buttonWithType：UIButtonTypeDetailDisclosure]; 
 rightButton.annotation = localAnnotation; 
  

localAnnotation是一个NSObject，但它实际上是一个MKAnnotation。我不明白为什么这不工作，但在运行时我得到这个错误：

  2010-05-27 10： 37：29.214 DonorMapProto1 [5241：207] ***  -  [UIButton注释]：发送到实例0x445a190的无法识别的选择器
 2010-05-27 10：37：29.215 DonorMapProto1 [5241：207] ***终止应用to uncaught exception'NSInvalidArgumentException'，reason：'***  -  [UIButton annotation]：unrecognized selector sent to instance 0x445a190'
  
 
 
 
'
 
 
 
我不明白为什么它甚至看着UIButton，因为我已经子类化了所以它应该查看MyDetailButton类来设置注释属性。我错过了一些很明显的东西。 ）
 
 
 
感谢您提供任何帮助，您可以提供
 
 
 
 Ross 
解决方案
 UIButton是一个类集群，这意味着Apple的实现 buttonWithType：像这样：
  +（id）buttonWithType：（UIButtonType）t {
 switch（t）{
 case UIButtonTypeDetailDisclosure：
 return [[[PrivateDetailDisclosureButtonClass alloc] init] autorelease]; 
 case ... 
} 
} 
  
调用 [MyDetailButton buttonWithType：UIButtonTypeDetailDisclosure]; 您没有得到 MyDetailButton 的实例， code> PrivateDetailDisclosureButtonClass （或任何苹果实际调用它）。
 
 
 
但请注意， >如果你用 UIButtonTypeCustom （至少在运行v3.0的模拟器中）调用它，就可以实例化 buttonWithType  ：
  // LGButton是UIButton的一个简单的子类
 LGButton * testBtn = [LGButton buttonWithType：UIButtonTypeCustom]; 
 LGButton * testBtn2 = [LGButton buttonWithType：UIButtonTypeDetailDisclosure]; 
 NSLog（@testBtn：％@，testBtn2：％@，[testBtn class]，[testBtn2 class]）; 
 //输出：testBtn：LGButton，testBtn2：UIButton 
  
 
I've created a sub class of UIButton:
//
//  DetailButton.h
#import <Foundation/Foundation.h>
#import <MapKit/MapKit.h>

@interface MyDetailButton : UIButton {
    NSObject *annotation;
}

@property (nonatomic, retain) NSObject *annotation;


@end

//
//  DetailButton.m
//


#import "MyDetailButton.h"


@implementation MyDetailButton


@synthesize annotation;

@end
I figured that I can then create this object and set the annotation object by doing the following:
MyDetailButton* rightButton = [MyDetailButton buttonWithType:UIButtonTypeDetailDisclosure];
rightButton.annotation = localAnnotation;
localAnnotation is an NSObject but it is really an MKAnnotation.  I can't see why this doesn't work but at runtime I get this error:
 2010-05-27 10:37:29.214 DonorMapProto1[5241:207] *** -[UIButton annotation]: unrecognized selector sent to instance 0x445a190
2010-05-27 10:37:29.215 DonorMapProto1[5241:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** -[UIButton annotation]: unrecognized selector sent to instance 0x445a190'
'

I can't see why it's even looking at UIButton because I've subclassed that so it should be looking at the MyDetailButton class to set that annotation property.  Have I missed something really obvious.  It feels like it :)

Thanks in advance for any help you can provide

Ross
解决方案
UIButton is a class cluster, which implies that Apple's implementation of buttonWithType: probably looks something like this:
+(id)buttonWithType:(UIButtonType)t {
  switch (t) {
    case UIButtonTypeDetailDisclosure:
      return [[[PrivateDetailDisclosureButtonClass alloc] init] autorelease];
    case ...
  }
}
So when you call [MyDetailButton buttonWithType:UIButtonTypeDetailDisclosure]; you don't get an instance of MyDetailButton, you get an instance of PrivateDetailDisclosureButtonClass (or whatever Apple actually calls it).

Note, however, that you can get buttonWithType to instantiate a subclass if you call it with UIButtonTypeCustom (At least in the simulator running v3.0):
// LGButton is a straightforward subclass of UIButton
LGButton *testBtn = [LGButton buttonWithType:UIButtonTypeCustom];
LGButton *testBtn2 = [LGButton buttonWithType:UIButtonTypeDetailDisclosure];
NSLog(@"testBtn: %@, testBtn2: %@", [testBtn class], [testBtn2 class]);
// Output: testBtn: LGButton, testBtn2: UIButton


                        
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