核心数据获取请求的复杂排序 [英] Complex sorting for core-data fetch request

问题描述

我有一个属性为的 NSEntity （ Cloth c $ c>），它从预定义的 NSString 值填充，即Poncho，Jacket，Coat，Gown，Top，Suit等。

I have an NSEntity (Cloth) with an attribute (type) which is filled from a list of predefined NSString values i.e. Poncho‎, Jacket, Coat, Gown, Top, Suit, etc.

我想获取所有的Cloth记录，使记录基于 type 的定义顺序排序。即，所有Poncho的记录在顶部，然后是夹克，然后是大衣，然后是大衣，然后是顶部，然后是西装等。

I want to fetch all the Cloth records such that the records are ordered based on a defined order for type. i.e. All the records for Poncho‎ are on top, then Jacket, then Coat, then Gown, then Top, then Suit, etc.

Poncho‎ …
Poncho‎ …
Poncho‎ …
Jacket … 
Jacket … 
Coat …
Coat …
Coat …
Gown …  
Gown …  
Top …
Top …
Top …
Top …
Suit …  
Suit … 

此订单不是升序或降序，而是自定义。如何获取 Cloth 记录，以便以此（定义）顺序返回？

This order is not ascending or descending, rather it's custom. How can I fetch the Cloth records such that they are returned in this (defined) order?

推荐答案

实现自定义顺序的唯一方法是引入 NSNumber 类型的新属性来跟踪订单。

The only way to implement a custom order is to introduce a new attribute of type NSNumber to keep track of the order.

[似乎在类别字符串（Poncho等）后面有更多的文本，所以你实际上有很多唯一的字符串， ]

[It seems that there is more text after the category string (Poncho, etc), so that you actually have many unique strings that all have to follow a custom order, only that they are grouped by first word.]

如果你真的想将这个逻辑与其他数据分开，你可以创建一个新的实体与属性 name 和 sortOrder 的ClothType Cloth 实体。

If you really want to separate this logic from the rest of the data, you can create a new entity ClothType with attributes name and sortOrder and have a relationship with your Cloth entity.

另一种方案是将排序属性乘以每个主要类别的10000，并为同一类别的每个后续类别添加1。

Another scheme is to multiply the sort attribute with, say, 10000 for every "primary" category and add 1 for each subsequent one of the same category.

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