核心数据子查询谓词 [英] Core data subquery predicate

问题描述

我有两个实体。

[League]< ---- >> [Game]

游戏有一个属性 kickOffDate 。

我想使用一个谓词来返回所有 Leagues c $ c>

我使用这个谓词...

  // startOfDay和endOfDay是分别返回给定日期的函数，分别为00:00:00和23:59:59 
 NSPredicate * startOfDayPredicate = [NSPredicate predicateWithFormat ：@SUBQUERY（games，$ g，$ g.kickOffDate> =％@）。@ count> 0，[self startOfDay：[NSDate date]]]; 
 NSPredicate * endOfDayPredicate = [NSPredicate predicateWithFormat：@SUBQUERY（games，$ g，$ g.kickOffDate< =％@）。@ count> 0，[self endOfDay：[NSDate date]]]; 
 
 NSPredicate * compoundPredicate = [NSCompoundPredicate andPredicateWithSubpredicate：@ [startOfDayPredicate，endOfDayPredicate]]; 
  

但是，当我使用这个，我似乎没有得到任何结果。

我是否正确写了谓语？

有更好的方法吗？

  [NSPredicate predicateWithFormat：@SUBQUERY（games，$ g，$ g.kickOffDate> =％@ AND $ g.kickOffDate< =％@）。@ count> 0，[self startOfDay：[NSDate date] ]，[self endOfDay：[NSDate date]]]; 
  

==联赛的开赛日期在指定范围内

您的解决方案相当于：

  [NSPredicate predicateWithFormat：@ ANY games.kickOffDate> =％@ AND ANY games.kickOffDate< =％@，start，end]; 
  

==联盟有一个游戏，在给定日期后开始游戏，给定日期（可以是不同的游戏或相同的游戏）

这应该返回比你喜欢的更多结果。

编辑：

正如@Martin R建议，您应该验证您的数据确实包含联赛回答谓词以测试它。

如果仍未得到结果，请检查请求执行期间是否有错误，并且您的数据堆栈已正确初始化。

I'm trying to get a subquery predicate to work and I'm struggling.

I have two entities.

[League] <---->> [Game]

Game has a property kickOffDate.

I'd like to use a predicate to return all Leagues that have at least one Game with a kickOffDate today.

I am using this predicate...

// startOfDay and endOfDay are functions to return the given date with 00:00:00 and 23:59:59 respectively
NSPredicate *startOfDayPredicate = [NSPredicate predicateWithFormat:@"SUBQUERY(games, $g, $g.kickOffDate >= %@).@count > 0", [self startOfDay:[NSDate date]]];
NSPredicate *endOfDayPredicate = [NSPredicate predicateWithFormat:@"SUBQUERY(games, $g, $g.kickOffDate <= %@).@count > 0", [self endOfDay:[NSDate date]]];

NSPredicate *compoundPredicate = [NSCompoundPredicate andPredicateWithSubpredicates:@[startOfDayPredicate, endOfDayPredicate]];

However, when I use this I don't seem to get any results.

Have I written the predicate correctly?

Is there a better way of doing this?

解决方案

Have you tried (untested):

[NSPredicate predicateWithFormat:@"SUBQUERY(games, $g, $g.kickOffDate >= %@ AND $g.kickOffDate <= %@).@count > 0", [self startOfDay:[NSDate date]],[self endOfDay:[NSDate date]]];

== League that have a game with a kick-off date in a given range

Your solution is equivalent to:

[NSPredicate predicateWithFormat:@"ANY games.kickOffDate >= %@ AND ANY games.kickOffDate <= %@",start,end];

== League that have a game that start after a given date and have a game that start before a given date (could be different games, or the same game)

Which should return more results than you like.

Edit:
As @Martin R suggested, you should verify that your data does indeed include a League answering the predicate to test it.
If you still get no results, check to see if there were errors during execution of the request and your data-stack is properly initialized.

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