自动@property合成不适用于NSManagedObject子类 [英] Automatic @property synthesize not working on NSManagedObject subclass

问题描述

昨晚更新到适用于iOS6的最新版Xcode 4.5后，我收到类似的警告和错误

After updating to the newest Version of Xcode 4.5 for iOS6 last night, i get Warnings and Errors like this

Property'mapAnnotation'要求方法'mapAnnotation'定义
- 使用@synthesize，@ dynamic或在此类实现中提供方法实现

Property 'mapAnnotation' requires method 'mapAnnotation' to be defined - use @synthesize, @dynamic or provide a method implementation in this class implementation

因为缺少@synthesize语句，甚至是关于未知iVars的错误，如果我使用它们。

because of missing @synthesize Statements, and even Errors about unknown iVars if i use them.

问题是，我认为自从Mountain Lion发布的上一个Xcode Update到4.5以来，没有必要编写这些@synthesize语句，并且我的所有项目都工作了没有他们之前我昨晚更新了Xcode（我已经从我的文件中删除了一大堆@synthesize语句）
它甚至还在Release-Notes中：

The thing is, i thought it was not necessary to write these @synthesize statements since the last Xcode Update to 4.5 that came out with Mountain Lion, AND all my projects worked without them before i've updated Xcode last night (i've deleted a whole bunch of @synthesize statements from my files back then) It's even still in the Release-Notes:

•使用属性时默认生成Objective-C @synthesize命令。

• Objective-C @synthesize command is generated by default when using properties.

所以我很困惑，我错过了一个新的项目设置，它会自动生成@synthesize生成？

So i'm confused, am i missing a new Project-Setting that turns automatic @synthesize generation on?

但是当我创建一个新项目并尝试它时它甚至都没有工作

But it's not even working when i create a new Project and try it

推荐答案

我遇到了同样的问题并找到了原因和解决方案。

I faced the same problem and found the reason and the solution.

如果你看一下iOS 6 SDK中NSManagedObject的头文件，你会看到NS_REQUIRES_PROPERTY_DEFINITIONS强制类为属性指定@dynamic或@synthesize。

If you look at the header file of NSManagedObject in iOS 6 SDK, you'll see "NS_REQUIRES_PROPERTY_DEFINITIONS" which forces classes to specify @dynamic or @synthesize for properties.

（您可以在iOS 5.1和iOS 6.0之间的API差异中看到NS_REQUIRES_PROPERTY_DEFINITIONS。）

(You can see the NS_REQUIRES_PROPERTY_DEFINITIONS in the API diff between iOS 5.1 and iOS 6.0.)

这是因为编译器必须知道您是希望属性是动态的还是合成的，特别是在NSManagedObject类的子类的实现中。

This is because the compiler has to know if you want a property to be dynamic or synthesized especially in the implementation of a subclass of NSManagedObject class.

我可以简单地为NSManagedObject子类中除@dynamic之外的属性显式添加@synthesize行来解决这个问题。

I could solve this problem simply by adding the @synthesize lines explicitly for the properties other than @dynamic in NSManagedObject subclasses.

这篇关于自动@property合成不适用于NSManagedObject子类的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！