为什么声明的属性同时使用保留和只读? [英] Why does a declared property use both retain and readonly?

问题描述

我注意到Apple的一些示例在属性上同时包含了retain和readonly修饰符.如果在使用readonly修饰符时没有生成设置器，那么包含retain有什么意义?

I've noticed that some of Apple's examples include both a retain and readonly modifier on properties. What's the point of including retain if no setter gets generated when we're using the readonly modifier?

示例:AnimatedTableView示例中的@property (retain, readonly) NSString *title;.

Example: @property (retain, readonly) NSString *title; from the AnimatedTableView sample.

推荐答案

您可以在类扩展中包含第二个私有读写声明.所有引用的内存管理方案都需要匹配IIRC，因此您会像只读，保留"这样愚蠢.

You can include a second, private readwrite declaration in a class extension. The memory management scheme for all references needs to match IIRC, so you get silliness like "readonly, retain".

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