将Obj-C 2.0属性与可变对象（如NSMutableArray）一起使用的最佳方法是什么？

I have an Obj-C 2.0 class that has an NSMutableArray property. If I use the following code, then the synthesised setter will give me an immutable copy, not a mutable one:I have an Obj-C 2.0 class that has an NSMutable