核心数据-NSPredicate-查找等于0但不为Null的属性

Question

There's no way this question hasn't been asked before but I cannot find a clear answer anywhere.

I have Core Data entities that have optional 'Integer 32' attributes. I'm trying to setup a predicate to retrieve all objects where that attribute equals zero but is not null.

attributes.power == nil AND attributes.power == 0

That's not doing the job. This is returning no results. Removing the first half of the compound predicate returns zeros and nulls.

Any help is greatly appreciated.

Answer 1

这可能是一个简单的错字，但我相信您想要谓词

attributes.power != nil AND attributes.power == 0

Answer 2

Why don't you try using optional 'String' attributes instead and then converting them to integers.
Alternatively, you can use a '-1' to indicate invalid values and put that as the default value of your attribute.