addObject后NSMutableArray为空 [英] NSMutableArray is empty after addObject

问题描述

我想将一个对象添加到NSMutableArray中：

I want to add an object into an NSMutableArray:

NSLog(@"Object text: %@", object.text);
NSLog(@"Object: %@", object);
[appdelegate.objects addObject:object];
NSLog(@"Objects array size: %i", [appdelegate.objects count]);

这是输出：

Object text: This is the text
Object: <Object: 0x6e762c0>
Objects array size: 0

这是怎么可能的，我添加了一个对象，下一行，它仍然是空的。 NSMutableArray 不是 nil ，因为这会引发异常。

How is this possible, I add an object, on the next line, it is still empty. The NSMutableArray is not nil, because that would raise an exception.

有人在猜吗？

推荐答案

如果它是 nil，它不会引发异常。如果它通常响应该消息，您仍然可以发送 nil 对象。在这种情况下，你只会得到0.我认为你没有分配数组。确保你这样做：

It would not raise an exception if it was nil. You can still message a nil object if it usually responds to that message. In this case, you'll just get 0. I think you're not allocating the array. Make sure you're doing this:

array = [[NSMutableArray alloc] init];

作为调试提示，如果您不确定对象的状态并想确定该对象确实存在并且可以使用，请使用 assert（appdelegate.objects）; 如果数组为nil，则代码将停止在此行执行。如果它没有在此行停止，那么您就知道该对象存在于内存中。

As a debugging tip, if you're unsure about the state of an object and want to make sure the object indeed exists and is ready to be used, use assert(appdelegate.objects); If the array is nil, your code will stop executing at this line. If it doesn't stop at this line, then you know the object exists in memory.

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