为什么在升级到Xcode 4.2之后MKAnnotation会显示警告 [英] Why after upgrading to Xcode 4.2 does MKAnnotation display a warning

问题描述

在Xcode 4.1中没有问题，但是升级到Xcode 4.2时，我收到以下警告:

In Xcode 4.1 there was no problem, but upgrading to Xcode 4.2 I get the following warning:

Property 'title' 'copy' attribute does not match the property inherited from 'MKAnnotation'
Property 'subtitle' 'copy' attribute does not match the property inherited from 'MKAnnotation'

我的代码:

@interface MyAnnotation : NSObject <MKAnnotation> {
    CLLocationCoordinate2D coordinate;
    NSString *subtitle;  
    NSString *title; 
}
@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;
@property (nonatomic, retain) NSString *subtitle;  
@property (nonatomic, retain) NSString *title; 

-(id)initWithCoordinate:(CLLocationCoordinate2D) coordinate;

@end

推荐答案

将其更改为:

@property (nonatomic, copy) NSString *subtitle;
@property (nonatomic, copy) NSString *title;

MKAnnotation协议声明

@property (nonatomic, readonly, copy) NSString *title;
@property (nonatomic, readonly, copy) NSString *subtitle;

您不应该更改属性的存储类型，唯一可以/应该进行的更改是从readonly到readwrite(如果需要)；

You shouldn't change the storage type of a property, the only change you can / should make is from readonly to readwrite if needed;

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