自动引用计数：指向非const类型“NSError *”的指针，没有明确的所有权 [英] Automatic Reference Counting: Pointer to non-const type 'NSError *' with no explicit ownership

问题描述

在更新我的一些代码以与iOS 5 SDK兼容时，我试图通过在Xcode中使用转换为Objective-C ARC来重构我的代码并收到错误。我的.h文件中的实例变量发生错误。

In updating some of my code to be in compatible with the iOS 5 SDK, I attempted to refactor my code by using "Convert to Objective-C ARC" in Xcode and received an error. The error occurs on an instance variable in my .h file.

NSError **_error;

错误显示指向非const类型'NSError *'，没有明确的所有权。我该如何解决这个问题？

The error says "Pointer to non-const type 'NSError *' with no explicit ownership." How might I fix this?

推荐答案

当存储 NSError 对象时实例变量你必须将它声明为一个简单的指针：

When storing NSError objects in an instance variable you have to declare it as a simple pointer:

@interface Foo : NSObject
{
    NSError *_errror;
}

NSError ** 仅用于间接从方法返回 NSError 对象到调用者。将它存储在实例变量中（可能）是一个错误。

NSError ** is only used to indirectly return NSError objects from a method to the caller. It is (probably) an error to store it in an instance variable.

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