为什么在提供 getter 和 setter 时需要编写 @synthesize? [英] Why do I need to write @synthesize when I provide getter and setter?

问题描述

所以属性的自动合成很棒.但是，当您同时提供 getter 和 setter 时，会出现错误.

So the auto synthesize of properties is awesome. However, when you provide both a getter and a setter, you get an error.

@property (strong, nonatomic) NSArray *testArray;

- (NSArray *)testArray {
    return _testArray;
}

- (void)setTestArray:(NSArray *)testArray {
    _testArray = testArray;
}

错误:使用未声明的标识符_testArray".

添加@synthesize testArray = _testArray; 解决问题.我只是想知道这是为什么?

Adding @synthesize testArray = _testArray; solves the problem. I am just wondering why this is?

推荐答案

当您同时提供 getter 和 setter 时，通常根本不需要实例变量，即当您只是转发这些消息或将数据存储在其他地方.

When you provide both getter and setter, there is often just no need for an instance variable at all, i.e. when you just forward those messages or store data in other places.

一旦其中一个缺失，就需要 ivar 来合成该功能.

As soon as one of them is missing, the ivar is needed to synthesize that functionality.

如果我没记错的话，对于只读属性，模拟假设也成立.

If I remember correctly, for readonly properties the analogue assumption holds as well.

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