问题描述
我有一个对象，它包含一个字典 JSONData 。从头文件和其他访问它的类，我希望这个属性只能是只读的和不可变的。
I have an object that holds a dictionary JSONData. From the header file, and to the other classes that'll access it, I want this property to only be read-only and immutable.
@interface MyObject : NSObject
@property (readonly, strong, nonatomic) NSDictionary *JSONData;
@end
但是，我需要 readwrite 和可变参数，如下所示，但不起作用：
However, I need it to be readwrite and mutable from the implementation file, like this, but this doesn't work:
@interface MyObject ()
@property (readwrite, strong, nonatomic) NSMutableDictionary *JSONData;
@end
@implementation MyObject
// Do read/write stuff here.
@end
有什么我可以做的，我要去的抽象？我看了其他问题，虽然我已经知道如何从 .h 和<$ c中创建属性 readonly $ c> readwrite 从 .m ，我找不到任何关于可变性的差异。
Is there anything I can do to enforce the kind of abstraction I'm going for? I looked at the other questions and while I already know how to make a property readonly from .h and readwrite from .m, I can't find anything about the difference in mutability.
推荐答案
您的实现中需要一个单独的私有可变变量。您可以覆盖getter以返回不可变对象。
You need a separate private mutable variable in your implementation. You can override the getter to return an immutable object.
@interface MyObject () {
NSMutableDictionary *_mutableJSONData;
}
@end
@implementation MyObject
// ...
-(NSDictionary *)JSONData {
return [NSDictionary dictionaryWithDictionary:_mutableJSONData];
}
// ...
@end
不需要实现setter，因为它是 readonly 。
No need to implement the setter, as it is readonly.
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