不同的实例化方法
这之间有什么区别：
AppDelegate *appDelegate = (AppDelegate *)[[NSApplication sharedApplication] delegate];
bookmarkObject *bookmark = (bookmarkObject *)[appDelegate.bookmarks objectAtIndex:i];
？
AppDelegate *appDelegate = (AppDelegate *)[[NSApplication sharedApplication] delegate];
bookmarkObject *bookmark = [[bookmarkObject alloc]init];
bookmark = [appDelegate.bookmarks objectAtIndex:i];
如果我不明白，这是一个大问题吗 两者都有效，但我不明白有什么区别
What is the difference between this:
AppDelegate *appDelegate = (AppDelegate *)[[NSApplication sharedApplication] delegate];
bookmarkObject *bookmark = (bookmarkObject *)[appDelegate.bookmarks objectAtIndex:i];
And
AppDelegate *appDelegate = (AppDelegate *)[[NSApplication sharedApplication] delegate];
bookmarkObject *bookmark = [[bookmarkObject alloc]init];
bookmark = [appDelegate.bookmarks objectAtIndex:i];
Does it is a big problem if I don't get it? Both work but I don't get the difference
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后者会泄漏内存。 objectAtIndex 返回一个自动释放的对象。在第二个示例中，您泄漏了 alloc 分配的内存。
正确的是第一个。如果您正在讨论实例化，那么通常有三种方法，一种是 [NSArray alloc] init]，另一个是 [NSArray array] - 这是 [[[NSArray alloc] init] autorelease] 和 [array] 的快捷方式copy] 创建一个副本。在所有情况下，除了自动释放的情况外，您必须自己释放内存。
Objective-C 是围绕传递指针构建的。因此，如果有某种方法返回指针，则无需分配或初始化任何内容。一般的经验法则 - 无论谁分配内存，都应该负责释放，否则必须自动释放。
The latter leaks memory. The objectAtIndex returns a auto-released object. In the second example you leak the memory allocated by alloc.
The proper one is the first. If you're discussing instantiation, then there're usually three methods, one, like [NSArray alloc] init], another [NSArray array] - which is a shortcut to [[[NSArray alloc] init] autorelease] and the [array copy] which creates a copy. In all cases, but autoreleased ones you have to release memory yourself.
Objective-C is built around passing pointers. Therefor if there's some method then returns pointer, you don't have to allocate or init anything. And a general rule of thumb - whoever allocates the memory, should be responsible for releasing, or it must be autoreleased.
好吧，它们或多或少会工作相同，因为您的第二个示例包含一个分配 (
bookmark = [[bookmarkObject alloc] init])，该分配立即被第二个分配 (mookmark = [appDelegate.bookmarks objectAtIndex:i];)。但第二个会泄漏内存。
Well, they would work the same, more or less, since your second example contains an assignment (
bookmark = [[bookmarkObject alloc] init]) that is immediately overruled by the second assignment (mookmark = [appDelegate.bookmarks objectAtIndex:i];).The second one leaks memory, though.