对核心数据实体的NSSets进行排序 - Objective-c [英] Sorting NSSets of a core data entity - Objective-c

问题描述

我想对核心数据NSSet的数据进行排序（我知道我们只能用数组做，但让我解释一下......）。我有一个实体用户与实体配方有很多关系。配方具有属性名称和ID。
我想得到这样的数据：

I would like to sort the data of a core data NSSet (I know we can do it only with arrays but let me explain...). I have an entity user who has a relationship to-many with the entity recipe. A recipe has the attributes name and id. I would like to get the data such that:

NSArray *id = [[user.recipes valueForKey:@"identity"] allObjects];
NSArray *name = [[user.recipes valueForKey:@"name"] allObjects];

如果我在两个数组中取索引1处的对象，它们对应于相同的配方......

if I take the object at index 1 in both arrays, they correspond to the same recipe...

谢谢

推荐答案

您需要先对食谱进行排序：

You need to sort the recipes first:

NSArray *sortDescriptors = [NSArray arrayWithObject:[NSSortDescriptor sortDescriptorWithKey:@"name" ascending:YES]];

NSArray *sortedRecipes = [[recipes allObjects] sortedArrayUsingDescriptors:sortDescriptors];

然后，您可以从已排序的配方数组中提取属性数组，结果将按排序顺序保留：

you can then extract an array of attributes from the sorted recipes array and the results will remain in sorted order:

NSArray *sortedNames = [sortedRecipes valueForKey:@"name"];
NSArray *sortedIdentities = [sortedRecipes valueForKey:@"identity"];

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