Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
728 views
in Technique[技术] by (71.8m points)

iphone - How to write a BOOL predicate in Core Data?

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

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

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

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];

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

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

From Predicate Programming Guide:

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"];

You can also check out the Predicate Format String Syntax.


与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...