Objective-C:知道是否释放了内存位置 [英] Objective-c: know if memory location was deallocated

问题描述

我已经为iOS项目实现了下载程序.它接受请求，下载完成后，由委托人响应目标.它是异步的，目标(显然)是一个弱引用，因此当下载完成时，如果不再分配目标，则将得到bad_acces. 我解决了添加一个方法(当使用该对象的对象被释放时调用)的方法，该方法在所有请求中搜索目标并将其设置为nil. 这与我想要的行为相去甚远(完全独立于其他对象:如果不再请求下载，它将被缓存:它没有停止下载的方法，只有优先级队列) 有一种安全的方法可以知道指针是否仍然指向有效的内存地址?

I have implemented a downloader for iOS projects. It accepts requests and, when download has finished, responds to a target by a delegate. It is asynchronous and the target is (obviously) a weak reference so when the download is complete, if the target is no more allocated, I've got a bad_acces. I've resolved adding a method (called when an object that use it is deallocated) that search for the target in all requests and sets it to nil. This is so far from the behavior I wanted (completly independent from other objects: if a download is no more requested it will be cached: it has no method to stop the download but only a priority queue) There is a safe way to know if a pointer still point to a valid memory address?

推荐答案

在回答您的问题时，没有一种很好的方法知道指针仍然有效(除了僵尸以外，它不是生产工具，环境解决方案，只是一个测试环境工具).但是，您不必担心我怎么知道这是否是一个悬空指针"，而应该只允许悬空指针从一开始就不会出现.

In answer to your question, there isn't a good way of knowing that a pointer is still valid (other than zombies, which isn't a production-environment solution, just a test-environment tool). But rather that worrying about "how do I know if this is a dangling pointer or not", you should just not allow dangling pointers from occurring in the first place.

创建下载程序时，您大概指定了一个委托.当作为委托的对象将消失时(例如，在其dealloc中)，它应该告诉下载程序将其委托属性设置为nil，从而消除了悬空的指针.

When your downloader was created, you presumably specified a delegate. When the object that is the delegate is going to disappear (e.g. in its dealloc), it should tell the downloader to set its delegate property to nil, thus eliminating the dangling pointer.

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