Objective-C - alloc 和 allocFromZone 之间的区别？

发布于 2024-12-15 12:05:14 字数 546 浏览 3 评论 0原文

可能的重复：
alloc 和 allocWithZone 之间有什么区别：？

我读了一篇文章提到使用 allocWithZone 通过使用更靠近对象本身的内存位置来帮助提高性能。这是真的吗？是否建议使用allocWithZone而不是alloc？ alloc 和 allocWithZone 有什么区别？

证明的例子是：

- (id)init
{
   if (self = [super init])
   {
      _myString = [[NSString allocWithZone:[self zone] init]];
   }

   return self;
}

原文

Possible Duplicate:
what is difference between alloc and allocWithZone:?

I read an article that mentions using allocWithZone helps improve performance by using a memory location closer to the object itself. Is this true? and is it recommended to use allocWithZone instead of alloc? What is the difference between alloc and allocWithZone?

The example proveded was:

- (id)init
{
   if (self = [super init])
   {
      _myString = [[NSString allocWithZone:[self zone] init]];
   }

   return self;
}

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眼睛会笑 2024-12-22 12:05:14

第一个 ARC 不允许在对象上调用 zone。由于所有事情都在朝着这个方向发展，这似乎是不使用allocWithZone 的充分理由。

据我所知，使用allocWithZone有一个很好的用途，它符合NSCopying。

@protocol NSCopying
- (id)copyWithZone:(NSZone *)zone;
@end

虽然您可以完全忽略区域参数，但我喜欢做类似的事情：

-(id)copyWithZone:(NSZone *)zone{
    SampleClass *copy = [[SampleClass allocWithZone:zone] init];
    copy->_myString = [_myString copyWithZone:zone];
    return copy;
}

除此之外，我认为没有什么比发布的上一个问题。

First ARC disallows calling zone on objects. Since all things are moving that way that seems a good enough reason to not use allocWithZone.

There is one good use that I know of to use allocWithZone, conforming to NSCopying.

@protocol NSCopying
- (id)copyWithZone:(NSZone *)zone;
@end

And while you can ignore the zone parameter alltogether, I like to do something like:

-(id)copyWithZone:(NSZone *)zone{
    SampleClass *copy = [[SampleClass allocWithZone:zone] init];
    copy->_myString = [_myString copyWithZone:zone];
    return copy;
}

Other than that I don't think there's much more to say than is posted the previous question.

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