objective-c - 需要澄清 addObjectsFromArray 函数

Question

我有以下代码(items 和 itemsCopy 都是 NSMutableArray 的):

//DO: populate items w/ 30 elements
[self.itemsCopy addObjectsFromArray:self.items];
//DO: remove all elements in items

结果

Begin Pass 1:
itemsCopy = 0
items = 30

End Pass 1:
itemsCopy = 30
items = 0

Begin Pass 2:
itemsCopy = 0
items = 30

End Pass 2:
itemsCopy = 30
items = 0

如何不断地将项目追加到 itemsCopy 的末尾？我希望场景如下所示:

Begin Pass 1:
itemsCopy = 0
items = 30

End Pass 1:
itemsCopy = 30;
items = 0;

Begin Pass 2:
itemsCopy = 30
items = 30

End Pass 2:
itemsCopy = 60
items = 0

Answer 1

通过保留刚刚填充 itemsCopy 属性的相同数组。无论您使用什么方法，它显然都会被重置为空数组。