如何设置NSPredicate以查找具有nil属性的对象 [英] How do I set up a NSPredicate to look for objects that have a nil attribute

问题描述

我有一个ManagedObject class，该类的成员之一是NSDate.我想显示未设置日期的类的所有对象.我尝试使用这样的谓词:

I have a ManagedObject class, and one of the members of the class is a NSDate. I would like to display all objects of the class for which the date is NOT set. I tried using a predicate like this:

NSPredicate *predicate = [NSPredicate predicateWithFormat: @"(date = NIL)"];

但是我仍然得到设置了date的对象.为此建立谓词的正确方法是什么?

But I still get objects where the date is set. What is the right way to set up a predicate for this?

推荐答案

我认为这是区分大小写的问题.您可以使用"nil"或"NULL"，但不能使用"NIL".这对我来说很好:

I think it's a case sensitivity issue. You can use "nil" or "NULL", but not "NIL". This works fine for me:

NSPredicate *eventWithNoEndDate = [NSPredicate predicateWithFormat:@"endDate = nil"];

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