我需要在 dealloc 中释放吗？

发布于 2024-08-23 00:27:56 字数 422 浏览 3 评论 0原文

在我正在学习的 iPhone 开发书中，他们使用 Interface Builder 来利用 IBOutlet 实例。一个例子是 UIButton。因此，他们在结构中添加了这样的内容：

 IBOutlet UIButton *whateverButton;

然后他们为 .h 中的每个属性添加一个 @property，并在 .m 中添加一个 @synthesize。

然后，他们在 .m 的 dealloc 中包含一个 release。两个问题：

是否需要发布？不是所有属性都已经自动处理了吗？
我如何检查引用计数以了解发生了什么，以进行调试......？

原文

In the book I'm studying from for iPhone dev, they utilize IBOutlet instances using the Interface Builder. An example would be a UIButton. So they add a thing in the struct like this:

 IBOutlet UIButton *whateverButton;

Then they add a @property for each of these in the .h, and a @synthesize in the .m.

Then they include a release in the dealloc of the .m. Two questions:

Is the release necessary? Aren't all properties already handled automatically?
How can I check the ref count to see what's happening, for debug purposes...?

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山色无中 2024-08-30 00:27:56

是否需要发布？不都是
已处理的属性
自动？

如果保留财产，则需要释放。当你声明一个@property和@synthesize它时，你得到的只是访问器，dealloc中没有特殊的自动行为。

另外，IBOutlet 并没有什么神奇之处——它只是 Interface Builder 的一个标记，用于查看您希望在 IB 中出现哪些属性。它只是一个空宏，按住 Cmd 键单击 IBOutlet 关键字即可查看其定义：

#ifndef IBOutlet
#define IBOutlet
#endif

IBAction 也是如此，它扩展为 void。

如何检查引用计数以查看
发生了什么，用于调试
目的...？

当我需要调试内存管理时，我通常只是在 dealloc 方法中设置一个断点或在那里记录一个字符串。在调用周围记录对象的 retainCount 也很有帮助，这些调用可能会对其产生可疑的影响。

了解 @synthesize 指令如何创建访问器也可能有所帮助。当您声明保留的@property并要求编译器对它们进行@synthesize时，您会得到类似这样的信息：

@property(retain) NSString *foo;
@synthesize foo;

- (void) foo {
    return foo;
}

- (void) setFoo: (NSString*) newFoo {
    // Try to think what would happen if this condition wasn’t
    // here and somebody called [anObject setFoo:anObject.foo].
    if (newFoo == foo)
        return;
    [foo release];
    foo = [newFoo retain];
}

这不完全是这样，但它已经足够接近了。现在应该更清楚为什么应该在 dealloc 中释放了。

Is the release necessary? Aren't all
properties already handled
automatically?

If the property is retained, the release is necessary. When you declare a @property and @synthesize it, all you get is the accessors, there is no special automatic behaviour in dealloc.

Also, there is nothing magical about IBOutlet – it’s just a marker for Interface Builder to see which properties you would like to appear in IB. It’s simply an empty macro, Cmd-click the IBOutlet keyword to see its definition:

#ifndef IBOutlet
#define IBOutlet
#endif

Same thing goes for IBAction which expands to void.

How can I check the ref count to see
what's happening, for debug
purposes...?

When I need to debug memory management, I usually simply set up a breakpoint in the dealloc method or log a string there. It is also helpful to log the retainCount of an object around the calls that might do something fishy with it.

It might also help to see how the @synthesize directive creates the accessors. When you declare a retained @property and ask the compiler to @synthesize them, you get something like this:

@property(retain) NSString *foo;
@synthesize foo;

- (void) foo {
    return foo;
}

- (void) setFoo: (NSString*) newFoo {
    // Try to think what would happen if this condition wasn’t
    // here and somebody called [anObject setFoo:anObject.foo].
    if (newFoo == foo)
        return;
    [foo release];
    foo = [newFoo retain];
}

This isn’t exactly the thing, but it’s close enough. Now it should be more clear why you should release in dealloc.

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