关于分配，保留，复制，澄清的澄清？ [英] Clarification on assign, retain, copy, strong?

问题描述

我仍然是Objective-C的新手，并且在设置属性时尝试找出使用assign，retain，copy，strong等的适当方法时遇到了一些困难。

I'm still new to Objective-C and having some difficulties trying to figure out the appropriate way to use assign, retain, copy, strong, etc. when setting a property.

例如，我声明了以下类型 - 我应该如何设置属性？

For example, I have the following types declared - how should I be setting the properties?

@property (nonatomic, ??) NSMutableArray *myArray
@property (nonatomic, ??) NSString *myString
@property (nonatomic, ??) UIColor *myColor
@property (nonatomic, ??) int *myIn
@property (nonatomic, ??) BOOL *myBOOL

谢谢.. ..

推荐答案

重申一下，它确实取决于上下文。在非ARC情况下：

To reiterate, it does depend on context. In an non-ARC situation:

@property (nonatomic, copy) NSMutableArray *myArray
@property (nonatomic, copy) NSString *myString
@property (nonatomic, retain) UIColor *myColor
//Note the change to an int rather than a pointer to an int
@property (nonatomic, assign) int myInt
//Note the change to an int rather than a pointer to an int
@property (nonatomic, assign) BOOL myBOOL

myArray上的副本是为了防止您设置的对象的另一个所有者进行修改。在一个ARC项目中，事情发生了一些变化：

The copy on myArray is to prevent modification by another "owner" of the object you set. In an ARC project, things change a bit:

@property (nonatomic, copy) NSMutableArray *myArray
@property (nonatomic, copy) NSString *myString
@property (nonatomic, strong) UIColor *myColor
//Note the change to an int rather than a pointer to an int
@property (nonatomic, assign) int myInt
//Note the change to an int rather than a pointer to an int
@property (nonatomic, assign) BOOL myBOOL

在您的情况下，更改主要是针对myColor。您不会使用保留，因为您不直接管理引用计数。 strong 关键字是一种断言属性所有权的方式，类似于 retain 。还提供了另一个关键字 weak ，通常用于代替对象类型的赋值。 Apple的一个弱属性的常见示例是代表。我建议您浏览过渡到ARC发行说明除了内存管理指南，还有一两次，因为还有更多细微差别很容易被SO帖子所覆盖。

The change is primarily to myColor in your situation. You wouldn't use retain as you aren't managing reference counting directly. The strong keyword is a way of asserting "ownership" of the property and similar to retain. An additional keyword is also provided, weak, that would typically be used in place of assign for object types. Apple's common example of a weak property is for delegates. I'd recommend going through the Transitioning to ARC Release Notes in addition to the Memory Management Guide a time or two as there is more nuance than can easily be covered in an SO post.

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