我在单身人士中使用保留或复制吗？ [英] Do I use retain or copy in my singleton?

问题描述

我读到某个地方，在对象中使用NSString，必须使用copy而不是retain。有人可以解释这是否正确以及为什么？

I read somewhere that with NSString in an object, one has to use copy instead of retain. Can someone explain if this is correct and why?

例如我对我的单身人士有以下声明：

For example I have the following declaration for my singleton:

#import <foundation/Foundation.h>
@class FaxRecipient;

@interface MyManager : NSObject {
    NSString *subject;
    NSString *reference;
    NSString *coverSheet;
    FaxRecipient *faxRecipient;

}

@property (nonatomic, retain) NSString *test1;
@property (nonatomic, retain) NSString *test2;
@property (nonatomic, retain) NSString *test3;
@property (nonatomic,retain) FaxRecipient *faxRecipient;



+ (id)sharedManager;

@end

推荐答案

我认为必须在必须的意义上是有点强大的。您可以使用复制或保留，但应 >通常使用复制为您的 NSString * 属性，因为：

I think "has to" in the sense of must is a little strong. You can use either copy or retain, but you should generally use copy for your NSString* properties because:

1. 你通常不希望在你的鼻子下改变一个字符串属性;


2. NSMutableString 是 NSString 的子类，所以有人可能会将 NSString * 属性设置为指向可变字符串，因此在你使用它时创建了更改字符串的可能性;


3. 对于像 NSString 这样的不可变类，复制操作结束无论如何，只保留原始对象。

1. You usually don't want a string property to change under your nose;
2. NSMutableString is a subclass of NSString, so it's entirely possible that someone might set your NSString* property to point to a mutable string, thus creating the potential for the string to be changed while you're using it;
3. For immutable classes like NSString, copy operations end up just retaining the original object anyway.

考虑到这三点，很难想出使用<$ c $的充分理由c>为您的 NSString 属性保留而不是 copy 。

Considering those three points, it's hard to think of a good reason to use retain instead of copy for your NSString properties.

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