iOS关于retainCount [英] iOS about retainCount

问题描述

现在我有一个ClassA : NSObject，然后在viewcontroller viewDidLoad中，查看下面的代码:

Now I have a ClassA : NSObject, and then in the viewcontroller viewDidLoad, look at the under code:

- (void)viewDidLoad {
    ClassA *a = [[ClassA alloc] init];
    NSLog(@"a retainCount = %d", [a retainCount]);
    ClassA *b = a;
    NSLog(@"a retainCount = %d b retainCount= %d ", [a retainCount],[b retainCount]);
    [a release];
    NSLog(@"a retainCount = %d b retainCount= %d", [a retainCount],[b retainCount]);
    [super viewDidLoad];
}

控制台输出如下:

2012-11-02 14:43:35.437 RetainCountTest[1043:207] a retainCount = 1
2012-11-02 14:43:35.439 RetainCountTest[1043:207] a retainCount = 1 b retainCount= 1  
2012-11-02 14:43:35.439 RetainCountTest[1043:207] a retainCount = 1 b retainCount= 1

我不明白我打电话给[a release]时为什么要使用[a retainCount］＝＝ 1?

I don't understand that when I call [a release], why the [a retainCount］＝＝ 1？

推荐答案

您永远不应该注意keepCount的注意.它们充其量是令人困惑的，而误导则是最坏的.只需确保它们正确地遵循保留/释放的内存管理规则，而不必考虑keepCounts.

You should never pay attention to retainCount's. They are at best confusing, and at worst misleading. One should just make sure that they follow memory management rules of retain/release correctly, and forget about retainCounts.

来自

此方法对于调试内存管理问题没有任何价值. 因为任何数量的框架对象都可能在其中保留了一个对象 为了保留对它的引用，同时自动释放 池可能在一个对象上保存任意数量的延迟释放，它 您不太可能从这种方法中获得有用的信息.

This method is of no value in debugging memory management issues. Because any number of framework objects may have retained an object in order to hold references to it, while at the same time autorelease pools may be holding any number of deferred releases on an object, it is very unlikely that you can get useful information from this method.

建议阅读

何时使用-retainCount?

看到OP的评论

来自可可核心内存管理规则

创建或复制对象时，其保留计数为1. 其他物件可能会表达您对物件的拥有权， 增加其保留计数.对象的所有者还可以 放弃他们的所有权权益，这会减少保留 数数.当保留计数变为零时，对象将被释放 (已毁).

When you create or copy an object, its retain count is 1. Thereafter other objects may express an ownership interest in your object, which increments its retain count. The owners of an object may also relinquish their ownership interest in it, which decrements the retain count. When the retain count becomes zero, the object is deallocated (destroyed).

如果有人读过这篇文章，他/她可能会想，哦，retainCount是天赐之物，我仅使用NSLog语句就可以看到对象的完整分配/保留/释放周期.但这实际上不是那样的.您不能说，您拥有所创建对象的唯一所有权.该对象可以由任何其他框架对象保留.通过释放，您只是放弃了所有权.只有在所有其他对象都删除其引用之后，该对象才会被释放.

If one read this, he/she might think, Oh retainCount is godsent, and I can see the complete alloc/retain/release cycle of an object just using an NSLog statement. But it doesn't actually works that way. You cannot say, you have sole ownership of object you create. That object might be retained by any other framework object. And by releasing you are just relinquishing your ownership. The object will get released only after all other objects remove their reference.

我不知道为什么它仍保留在公共API中.

I don't know why it remains in public API.

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