核心数据子顺序集 [英] Core Data Child Ordered Set

问题描述

我在核心数据中有两个具有父子关系的实体（订单和购物车）。生成的父类具有访问子记录的属性。

I have two entities (Order and Cart) in core data with a parent child relationship. The generated parent class has a property to access the child records.

@interface Order : NSManagedObject

@property(nonatomic, retain) NSOrderedSet *carts;

@end

说，购物车的字段为 x，是是否有可能告诉核心数据框架将上面的 carts 集合始终按x排序？

Say, Cart has a field 'x', is it possible to tell core data framework to keep the carts collection above always ordered by x?

推荐答案

不带有 NSOrderedSet 。如果您对孩子有逻辑上的排序，那么您完全不必理会 NSOrderedSet ，而不必理会它们。更改之后，您可以使用 NSSortDescriptor 将子级排序为 NSArray 。

Not with an NSOrderedSet. If you have a logical sort for your children then you should not bother with a NSOrderedSet at all and just leave them as unordered. After that change you can use a NSSortDescriptor to sort the children into an NSArray.

与 NSOrderedSet 相比，这将为您带来更好的性能，并让您按 x 。

That will yield better performance for you compared to a NSOrderedSet and will let you sort by x.

有序关系非常昂贵，除非有绝对必要，否则应避免。

Ordered relationships are very expensive and should be avoided unless there is an absolute necessity.

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