NSFetchRequest从Core Data iOS返回错误

Question

我试图在下面的代码中获取stateName并将其显示在标签中。 但是它总是返回错误。

-(NSArray *) getStateNameFromCode :(NSString *) stateCode
{
    NSManagedObjectContext *objectContext = [self managedObjectContext ];
    NSEntityDescription *entity = [NSEntityDescription entityForName:ENTITY_STATES inManagedObjectContext:objectContext];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"%K == %@", COLUMN_STATE_CODE, stateCode];
    NSLog(@"Predicate : %@" ,predicate);
    NSFetchRequest *fetchRequest = [[ NSFetchRequest alloc]init];

    [fetchRequest setEntity:entity];
    [fetchRequest setPredicate:predicate];

    NSArray *stateName  = [objectContext executeFetchRequest:fetchRequest error:Nil];
    if (stateName.count > 0)
    {
        return [stateName objectAtIndex:0];

    }

    return  nil ;

}

 self.labelTeams.text = [NSString stringWithFormat:@"%@\n" ,
                            [sharedController getStateNameFromCode:_checklist.stateHomeTeam]]
                            ;

OUTPUT：

 <States: 0xa571560> (entity: States; id: 0xa565300 <x-coredata://D6B54D51-4556-41E1-A372-F39EB871A076/States/p8> ; data: <fault>)

使用setreturnsobjectsasfaults = NO尝试过，但是那不起作用。 发现如此多的链接，其中大多数都说使用setreturns对象错误。 我杀了我的布莱恩。 任何想法将不胜感激。

问候，

Answer 1

尝试这个，

//return state name as NSString (assumes state name is string type)
-(NSString *) getStateNameFromCode :(NSString *) stateCode
{
    ....

    NSArray *states  = [objectContext executeFetchRequest:fetchRequest error:Nil];
    if (states.count > 0)
    {
        //Matched state object
        NSManagedObject *state = [states objectAtIndex:0];
        //or States *state = [states objectAtIndex:0];, if States is the NSManagedObject subclass name
        return //return name of state from state object, like state.name

    }

    return  nil ;

}

 self.labelTeams.text = [NSString stringWithFormat:@"%@\n" ,
                            [sharedController getStateNameFromCode:_checklist.stateHomeTeam]]
                            ;