CFStringRef到NSString ARC泄漏.为什么? [英] CFStringRef to NSString ARC leaking. Why?

问题描述

我一直在寻找在ARC中从CFStringRef转到NSString的正确方法，以避免内存泄漏，并且一些主要的投票建议表明:

I have been looking around for the correct way to go from CFStringRef to NSString in ARC to avoid memory leaks and some of the main voted answers suggest:

NSString * string = (__bridge NSString *)cfString;

我在这里使用这种方法，但是在对应用程序进行性能分析时，这种小方法仍然会导致内存泄漏.(见附图).

I am using that approach here but when profiling the app I still get a memory leak in this small method [see attached image].

因此，我不确定如何解决此问题.有人有解决这个问题的方法吗?

So, I am not sure how to fix this. Anybody has the solution to this problem?

谢谢

因此，显然在返回之前添加CFRelease(ext)可以修复泄漏.问题是我不完全理解原因.我以为那行:

So, apparently adding the CFRelease(ext) before the return fixed the leak. Problem is I don't think I fully understand the reason. I thought that the line:

NSString * extension = (__bridge NSString*)ext

将拥有Core Foundation ext字符串的所有权并处理发布. 有人能确切解释这里发生了什么吗?

Would take ownership of the Core Foundation ext string and handle the release. Can anybody explain what is going on here exactly?

推荐答案

按照事实上的标准"可可命名约定，名称中包含Create或Copy的函数将返回带有引用计数的对象of1.您必须将此参考计数转移到ARC-land，以便ARC可以处理它.为此，请使用__bridge_transfer关键字.

As per the de-facto "standard" Cocoa naming convention, functions that contain Create or Copy in their name return an object with a reference count of 1. You have to transfer this reference count into ARC-land so that ARC can take care of it. You use the __bridge_transfer keyword for this purpose.

NSString *string = (__bridge_transfer NSString *)cfString;

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