Objective-C属性-保留和分配之间的区别 [英] Objective-C Property - Difference Between Retain and Assign

问题描述

我认为我缺少有关属性属性的信息. 首先，我无法理解retain和assign之间的区别.

I think I am missing something about property attributes. First, I can't understand the difference between retain and assign.

如果我使用assign，该属性是否将setter和getter的retain计数器增加1，我是否都需要对它们同时使用release?

If I use assign, does the property increase the retain counter by 1 to the setter and also to the getter, and do I need to use release to both of them?

这如何与readwrite或copy一起使用?从retain计数的角度来看.

And how does this work with readwrite or copy? From the view of a retain count.

在尝试处理属性(设置者和获取者)后，何时需要使用release

I am trying to understand when i need to use release after working with a property (setter and getter)

@property (readwrite,assign) int iVar; 

assign在这里做什么?

两者之间有什么区别

@property (readwrite,assign) int iVar;

和

@property (readwrite,retain) int iVar;

和

@property (readwrite) int iVar;

非常感谢...

推荐答案

@property(readwrite，assign)之间有什么区别int iVar;到@property(读写，保留)int iVar；到@property(readwrite)int iVar;

what is the different between : @property (readwrite,assign) int iVar; to @property (readwrite,retain) int iVar; to @property (readwrite) int iVar;

@property (readwrite,assign) sometype aProperty;的设置器在语义上等效于

The setter for @property (readwrite,assign) sometype aProperty; is semantically equivalent to

-(void) setAProperty: (sometype) newValue
{
    ivar = newValue;
}

上面的内容或多或少会给您带来帮助

The above is more or less what you will get if you put

@asynthesize aProperty = ivar;

在您的实施中.

@property (readwrite,retain) sometype aProperty;的设置器在语义上等效于

The setter for @property (readwrite,retain) sometype aProperty; is semantically equivalent to

-(void) setAProperty: (sometype) newValue
{
    [newValue retain];
    [ivar release];
    ivar = newValue;
}

很显然，保留或释放int毫无意义，因此某类型必须为id或SomeObjectiveCClass*

Clearly, it makes no sense to retain or release an int, so sometype must be either id or SomeObjectiveCClass*

@property (readwrite,copy) sometype aProperty;的设置器在语义上等效于

The setter for @property (readwrite,copy) sometype aProperty; is semantically equivalent to

-(void) setAProperty: (sometype) newValue
{
    sometype aCopy = [newValue copy];
    [ivar release];
    ivar = aCopy;
}

在这种情况下，不仅某种类型必须是目标C类，而且它必须响应-copyWithZone:(或等效地实现NSCopying).

In this case, not only must sometype be an objective C class but it must respond to -copyWithZone: (or equivalently, implement NSCopying).

如果省略保留，分配或复制，则默认为分配.

If you omit retain or assign or copy, the default is assign.

顺便说一句，我通过不考虑由于属性也未指定nonatomic而发生的锁定来简化了上述操作.

By the way, I have simplified the above by not considering the locking that occurs because the properties don't also specify nonatomic.

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