Question

首先,这是我第一个问题,

你们有没有注意到 NSPPrevituate的怪异行为数学功能?

举个例子:

1) 我有离境舱与接口:

@interface OTDeparture : NSManagedObject
@property (nonatomic, retain) NSNumber * position;
@end

i 2) 创建获取请求时使用前提 :

NSPredicate *predicate=[NSPredicate predicateWithFormat:@"(position-1)*(position-1) > 0"];

结果总是零对象(预言总是 NO) 。格式“ (2-1) * (2-1) & gt; 0” 和“ (position-1) *position & gt; 0” 也会做同样的事情。

这些上游格式工作如预期(返回对象:预期返回对象):

"2*(position-1) > 0"
"2*2 > 0"
"position-3 > 0"

我做错什么了,还是这真的是虫子?

Answer 1

Seems like you re right, there are some in CoreData :(( I have the same issue - Is there any way to use NSPredicate to filter objects using distance calculation between points in CoreData seems like the only way to receive what you want is to use predicateWithBlock: method, though I haven t tried it myself yet. And note that predicateWithBlock: works only for in-memory stores. So most probably you will end up filtering the data by just going through all entities, of course you can try to make at least some filtering before doing this.

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