错误:可写原子属性无法将合成的 setter/getter 与用户定义的 setter/getter 配对 [英] error: writable atomic property cannot pair a synthesized setter/getter with a user defined setter/getter

问题描述

我最近尝试编译一个旧的 Xcode 项目(以前编译得很好)，现在我看到了很多这种形式的错误:

I recently tried to compile an older Xcode project (which used to compile just fine), and now I'm seeing a lot of errors of this form:

错误:可写原子属性someProperty"无法将合成的 setter/getter 与用户定义的 setter/getter 配对

导致这些错误的代码模式始终如下所示:

The code pattern which causes these errors always looks like this:

// Interface:

@property (retain) NSObject * someProperty;

// Implementation:

@synthesize someProperty; // to provide the getter
- (void)setSomeProperty:(NSObject *)newValue
{
    //..
}

我知道为什么会产生错误.我告诉编译器合成我的属性访问器(getter 和 setter)，然后立即手动覆盖 setter.这段代码总是有点臭.

I can see why the error is being generated. I tell the compiler to synthesize my property accessors (both getter and setter), and then immediately afterward I override the setter manually. That code has always smelled a little off.

那么，这样做的正确方法是什么?如果我使用 @dynamic 而不是 @synthesize，我将不得不编写 getter.只有这样吗?

So, what is the proper way to do this? If I use @dynamic instead of @synthesize, I will have to write the getter as well. Is that the only way?

推荐答案

我遇到了同样的问题，经过一番研究，我对这个问题的结论如下:

I had the same problem and after doing a bit of research, here is my conclusion about this issue:

编译器警告您有关您声明为原子的 @property(即通过省略 nonatomic 关键字)，但您提供了如何同步访问的不完整实现到那个属性.

The compiler warns you about a @property that you declared as atomic (i.e. by omitting the nonatomic keyword), yet you provide an incomplete implementation of how to synchronize access to that property.

要使该警告消失:

如果您将 @property 声明为原子，请执行以下操作之一:

If you declare a @property to be atomic then do one of the following:

• 使用 @dynamic 或;
• 使用 @synthesize 并保留合成的 setter 和 getter 或；
• 提供 setter 和 getter 的手动实现(不使用上述指令之一).

• use @dynamic or;
• use @synthesize and keep the synthesized setter and getter or;
• provide a manual implementation of both the setter and the getter (without using one of the above directives).

如果您使用 (nonatomic) 声明 @property，那么您可以混合使用手动和合成的 getter 和 setter 实现.

If you declare the @property with (nonatomic) then you can mix manual and synthesized implementations of getters and setters.

更新:关于属性自动合成的说明

从 LLVM 4.0 开始，CLang 为不是 @dynamic 的声明属性提供自动合成.默认情况下，即使您省略了 @synthesize，编译器也会为您提供 getter 和 setter 方法.但是，原子属性的规则仍然相同:要么让编译器同时提供getter和setter，要么自己实现它们both！

As of LLVM 4.0, CLang provides auto-synthesis for declared properties that are not @dynamic. By default, even if you leave out the @synthesize, the compiler will provide getter and setter methods for you. However, the rule for atomic properties is still the same: Either let the compiler provide both the getter and the setter, OR implement them both yourself!

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