iOS Get objects from CoreData sorted by primary key

Question

I have saved data into db using CoreData. I need to fetch data from my table in same order that it was saved. Inside table it is ordered by Z_PK - hidded CoreData key. How can I

Answer 1

Use a sort descriptor with self as the sort key. The underlying SQL will have ORDER BY t0.Z_PK.

Answer 2

There is no proper method in core data framework to sort object by primary key, but I think we can use objectID as a the primary key and sort by objectID. ObjectID for a particular object would always increase.. thus you can use below method

/*!
@param <NSManagedObject> array 
@return <NSManagedObject> sortedarray
*/

+ (NSArray *) sortManagedObjectArrayByObjectID:(NSArray *) array {

    NSArray *compareResult = [array sortedArrayUsingComparator:^NSComparisonResult(NSManagedObject *obj1, NSManagedObject *obj2) {

        NSString *s = [obj1.objectID.URIRepresentation lastPathComponent];
        NSString *r = [obj2.objectID.URIRepresentation lastPathComponent];
        return [s compare:r];

    }];

    return compareResult;

}

Hope this would help

Answer 3

Anything not exposed to you by the Core Data framework is an implementation detail. The fact that Z_PK exists, and currently suits your purposes, cannot be relied upon.

If creation/save order is important to your model, then it should be included in your model. There's really nothing else to it.