apple cocoa内存管理笔记

核心提示：id delegate;}@end拷贝后的内存位置图如下：假设从supercalass继承了NSCopying，但是父类没有实现NSCopying，apple cocoa内存管理笔记(2)，那么你要实现的话必须拷贝super的实例，同样包括自己声明的变量，并且在你的类中你声明了一些实例变量，那么你必须实现copyWit

id delegate;

}

@end

拷贝后的内存位置图如下：

假设从supercalass继承了NSCopying，但是父类没有实现NSCopying，那么你要实现的话必须拷贝super的实例，同样包括自己声明的变量。一般情况下安全的方式是使用如alloc,

init..., and set methods

另外一方面，如果super类已经实现了NSCopying，并且在你的类中你声明了一些实例变量，那么你必须实现copyWithZone:

如果类没有继承NSCopying的行为，那么实现copyWithZone: using alloc,init..., and set methods.下面是一个例子

- (id)copyWithZone:(NSZone *)zone

{

Product *copy = [[[self class] allocWithZone: zone]

initWithProductName:[self productName]

price:[self price]];

[copy setDelegate:[self delegate]];

return copy;

}

有些继承了NSCopying behavior的类,但是他们的super类的实现可能使用了 NSCopyObject function. NSCopyObject creates an exact shallow copy of an object

by copying instance variable values but not the data they point to. 举个例子, NSCell类采用如下的方式实现copyWithZone

- (id)copyWithZone:(NSZone *)zone

{

NSCell *cellCopy = NSCopyObject(self, 0, zone);

/* Assume that other initialization takes place here. */

cellCopy->image = nil;

[cellCopy setImage:[self image]];

return cellCopy;

}

在上面的实现采用的是浅拷贝

对可变长度的对象的拷贝实现 ，要继承NSMutableCopying

Core Foundation Objects in Cocoa中的内存管理

Core Foundation's memory allocation policy is that you need to release values returned by functions with “Copy” or “Create” in their name; you should not release values returned by functions that do not have “Copy” or “Create” in their name.

举几个例子

NSString *str = [[NSString alloc] initWithCharacters: ...]; ... [str release];

is equivalent to