How do you request Core Data to get only one attribute?

Question

I just need to get an attribute from a single row of the table:

 name  | id   | idade  | aprov|repro| sala | 
_______|______|________|______|_____|______| 
John   |  32  |    15  |   A  |     | 155  | 

Following the table above would be the field idade containing the element 15.

How can I do this using Core Data?

In case this app is for iOS.

Answer 1

To get only the column age you define the method setPropertiesToFetch: of your object NSFetchRequest, something like that:

[request setPropertiesToFetch:[NSArray arrayWithObjects:@"idade", nil]];

And to make the filter, a NSPredicate:

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id == %d", 32];
[request setPredicate:predicate];

And so performs the rest of your request that will return a single object, according to the id.