NSManagedObjects中的可变集？ [英] Mutable sets in NSManagedObjects?

问题描述

自动生成的 NSManagedObject 属性的标准声明声明了许多关系，如下所示：

The standard declaration for an autogenerated NSManagedObject property declares to-many relationships like this:

@property (nonatomic, retain) NSSet *somethings;
...
@dynamic somethings;

将声明更改为 NSMutableSet ？ CoreData组件是否仍能正常运行？

Would it be safe to change that declaration to an NSMutableSet? Would the CoreData component still function correctly?

根据 @dynamic 判断，probaby不关心使用 NSSet 子类，而不是 NSSet ，但我不想重写大量代码，

Judging by the @dynamic, it probaby doesn't care if I use an NSSet subclass rather than an NSSet, but I don't want to rewrite a lot of code only to find out it doesn't work.

推荐答案

根据Apple的核心数据编程指南，声明为NSSet。

According to Apple's Core Data Programming Guide, this should always be declared as a NSSet.

如果你想要一个可变代理（基本上是核心数据集的可变版本，工作原理完全一样），那么你将使用函数 mutableSetValueForKey 像这样：

If you want a mutable proxy (which is basically the mutable version of the core data set and works exactly the same) then you would use the function mutableSetValueForKey like this:

// myManagedObject is the managed object that has the somethings property.
NSMutableSet *mutableSomethings = [myManagedObject mutableSetValueForKey:@"somethings"];

mutableSomethings NSMutableSet和 somethings 将被更新，KVO方法将被适当地调用。

mutableSomethings can then be modified as a standard NSMutableSet andsomethings will be updated and KVO methods will be appropriately called.

注意，已经在核心数据生成的访问器中提供了可变集（例如 addSomethingsObject 和 removeSomethingsObject ），因此在许多情况下，无需使用代理。

Note however, that many features of the mutable set (such as addSomethingsObject and removeSomethingsObject) are already provided in the core data generated accessors so in many cases you don't need to use the proxy.

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