如何在 Core Data 中编写 BOOL 谓词? [英] How to write a BOOL predicate in Core Data?

问题描述

我有一个 BOOL 类型的属性，我想搜索该属性为 YES 的所有托管对象.

I have an attribute of type BOOL and I want to perform a search for all managed objects where this attribute is YES.

对于字符串属性，它很简单.我创建了一个这样的谓词:

For string attributes it is straightforward. I create a predicate like this:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"userName = %@", userName];

但是如果我有一个名为 selected 的 bool 属性并且我想为此做一个谓词，我该怎么做?我可以做这样的事情吗?

But how do I do this, if I have a bool attribute called selected and I want to make a predicate for this? Could I just do something like this?

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"selected = %@", yesNumber];

或者我是否需要其他格式说明符并只通过YES?

Or do I need other format specifiers and just pass YES?

推荐答案

来自 谓词编程指南:

您指定并测试布尔值是否相等，如以下示例所示:

You specify and test for equality of Boolean values as illustrated in the following examples:

NSPredicate *newPredicate = [NSPredicate predicateWithFormat:@"anAttribute == %@", [NSNumber numberWithBool:aBool]];
NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"anAttribute == YES"];

您还可以查看谓词格式字符串语法.

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