iPhone内存管理 [英] iPhone Memory Management

问题描述

我正在开发一个应用程序，我想确保我正确地管理内存并释放我应该做的一切。在我的viewDidLoad方法中，我分配一些变量来确定要应用于视图的背景（用于国际化），如果我不释放它们，应用程序就可以正常工作。

I'm working on an app and I'd like to make sure that I'm managing memory properly and releasing everything that I should. In my viewDidLoad method I allocate some variables in determining which background to apply to the view (for internationalization) and the app works fine if I don't release them.

问题是，如果我发布变量，应用程序将崩溃。 viewDidLoad中的代码如下：

The problem is that if I release the variables the app will crash. Code from viewDidLoad is below:

// Set the background image based on the phone's preferred language
NSString *language = [[NSLocale preferredLanguages] objectAtIndex:0];
NSString *backgroundImageName = [[NSString alloc] init];
backgroundImageName = [NSString stringWithFormat:@"background-%@.png",language];
self.view.backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:backgroundImageName]];

... do some more initialization stuff ...

// IF THE FOLLOWING ARE RELEASED THE APP WILL CRASH!!!
//[backgroundImageName release];
//[language release];

为什么发布backgroundImageName和语言变量导致应用程序崩溃？

Why would releasing the backgroundImageName and language variables cause the app to crash?

推荐答案

NSString *language = [[NSLocale preferredLanguages] objectAtIndex:0];

此处，语言不需要是因为 objectAtIndex：为你自动释放它而发布。按照惯例，如果您 alloc ed， new ed或，则拥有一个对象复制编辑它，否则你没有。

Here, language does not need to be released because objectAtIndex: autoreleases it for you. By convention, you own an object if you've alloced, newed, or copyed it, otherwise you don't.

self.view.backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:backgroundImageName]];

这里， UIColor 对象确实需要被释放（因为你 alloc ed it）。

Here, the UIColor object does need to be released (because you alloced it).

NSString *backgroundImageName = [[NSString alloc] init];
backgroundImageName = [NSString stringWithFormat:@"background-%@.png",language];

这里是 [[NSString alloc] init]返回的字符串确实需要发布（因为你已经 alloc ed it）。但是，下一行更改 backgroundImageName 以指向新的自动释放字符串，丢失对原始字符串的最后一次引用而不释放它（内存泄漏）。 backgroundImageName 不应该被释放，因为它已经被自动释放。

Here the string returned by [[NSString alloc] init] does need to be released (because you've alloced it). However, the next line changes backgroundImageName to point to that a new autoreleased string, losing the last reference to the original string without releasing it (a memory leak). backgroundImageName should not be released because it is already autoreleased.

你可以通过释放<$ c来避免泄漏$ c> UIColor 并消除未使用的字符串。例如：

You can avoid the leaks by releasing the UIColor and eliminating the unused string. For example:

NSString *backgroundImageName = [NSString stringWithFormat:@"background-%@.png",language];

...和...

UIColor* backgroundColor = [[UIColor alloc] initWithPatternImage:[UIImage imageNamed:backgroundImageName]];
self.view.backgroundColor = backgroundColor;
[backgroundColor release];

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