获取核心数据SQLite数据库的数量

Question

Using Core-Data to hold various information, one of which is a 'number' attribute (Int(16)). I try to take it out of the database using: number = (int)[info valueForKey:@"number"] ;

Unfortunately, this always gives some awful result, like 2895891275 when it should be returning 3.

Would appreciate any help, thanks!

Answer 1

valueForKey returns an object, not an int. The fact that you're having to cast it explicitly should be a warning sign. Try:

number = [[info valueForKey:@"number"] intValue];

Answer 2

To expand on @duskwuffs answer:

All values in Core Data are objects. When you set an attribute type to, say, Int16, Core Data will create an NSNumber object.

This code:

number = (int)[info valueForKey:@"number"]

... gives you a huge number because [info valueForKey:@"number"] returns an instance of NSNumber, an object, which you cast to an int. When you cast an object to an int you actually cast it's address in memory to an int and so end up with a large nonsensical number.