NSPredicate在关系实体中进行搜索

问题描述

我有一个名为Band的实体，它与类别实体具有多对多关系。 Category实体只包含一个categoryName字符串属性。

示例记录：

 乐队：
 bandName：Kiss 
 bandCategories： - > BandCategory：categoryName：Glam 
  - > BandCategory：categoryName：Rock 
  

如何使用NSPredicate搜索所有我的乐队，

根据，您需要指定categoryName的关键路径，并使用 ANY 或 ALL 说明符。

  NSString * category = @Rock 
 [NSPredicate predicateWithFormat：@ANY bandCategories.categoryName ==％@，category]; 
  

I have an entity called Band which has a to-many relationship to a Category entity. The Category entity just contains a categoryName string attribute.

An example record:

Band:       
  bandName: Kiss
  bandCategories:   -  > BandCategory:categoryName:Glam
                    -  > BandCategory:categoryName:Rock

How would I use NSPredicate to search thru all my Bands for bands which match the Rock category, for example?

解决方案

According to the NSPredicate Programming Guide you will need to specify the key path to categoryName with the ANY or ALL specifier.

NSString *category = @"Rock";
[NSPredicate predicateWithFormat:@"ANY bandCategories.categoryName == %@", category];

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