如何从保存为NSString的CoreData中读取日期？

Question

I have CoreData entity which contain an attribute dateUpdated (type NSString with format "2013-06-27").

When I want to read this value it returns nil .

Recipes *oldRecipe;
oldRecipe = [self getRecipeWithCode:i];
NSDateFormatter *dtFormatter = [[NSDateFormatter alloc] init];
[dtFormatter setDateFormat:@"yyyy-MM-dd"];

NSString *oDate = oldRecipe.dateUpdated; 
//after this oDate is nil
NSDate *oldDate = [dtFormatter dateFromString:oDate];

I have already checked value presence in entity with SQL Manager.

How can I correctly do it?

Answer 1

As it turned out in the discussion, the oldRecipe object is created in the getRecipeWithCode method using a temporary managed object context.

A managed object can only live in the context that it was created in. If the context is deallocated then oldRecipe will not be nil, but accessing its properties will always return nil.