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  • CoreData

    插入:

    - (void)insertCoreData2
    {
        NSManagedObjectContext *context = [self managedObjectContext];
        Orange *orange = [NSEntityDescription insertNewObjectForEntityForName:@"Orange" inManagedObjectContext:context];
        
        orange.color = @"org";
        NSError *error;
        BOOL b = [context save:&error];
        NSLog(@"%@",b?@"YES":@"NO");
    }

     查询:

    - (void)getByQuery
    {
        NSManagedObjectContext *context = [self managedObjectContext];
        NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
        [fetchRequest setEntity:[NSEntityDescription entityForName:@"Orange" inManagedObjectContext:context]];
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"color like[cd]'red'"];
        [fetchRequest setPredicate:predicate];
        [fetchRequest setFetchBatchSize:5];
        [fetchRequest setFetchOffset:0];
        [fetchRequest setFetchLimit:5];
        NSSortDescriptor *sortDesc = [[NSSortDescriptor alloc] initWithKey:@"color" ascending:YES];
        NSArray *sortDescriptors = [NSArray arrayWithObjects:sortDesc, nil];
        [fetchRequest setSortDescriptors:sortDescriptors];
        NSError *error;
        NSArray *fetchedItems = [context executeFetchRequest:fetchRequest error:&error];
        if (fetchRequest == nil) {
            NSLog(@"fetch request resulted in an error: %@,%@ ", error, [error userInfo]);
        }
        for (Orange *orange in fetchedItems) {
            NSLog(@"%@", orange.color);
        }
    }

     更新:

     NSFetchRequest* request=[[NSFetchRequest alloc] init];  
        NSEntityDescription* user=[NSEntityDescription entityForName:@"User" inManagedObjectContext:_myAppDelegate.managedObjectContext];  
        [request setEntity:user];  
        //查询条件  
        NSPredicate* predicate=[NSPredicate predicateWithFormat:@"name==%@",@"chen"];  
        [request setPredicate:predicate];  
        NSError* error=nil;  
        NSMutableArray* mutableFetchResult=[[_myAppDelegate.managedObjectContext executeFetchRequest:request error:&error] mutableCopy];  
        if (mutableFetchResult==nil) {  
            NSLog(@"Error:%@",error);  
        }  
        NSLog(@"The count of entry: %i",[mutableFetchResult count]);  
        //更新age后要进行保存,否则没更新  
        for (User* user in mutableFetchResult) {  
            [user setAge:[NSNumber numberWithInt:12]];  
              
        }  
        [_myAppDelegate.managedObjectContext save:&error];  
        [mutableFetchResult release];  
        [request release]; 
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  • 原文地址:https://www.cnblogs.com/apem/p/4349524.html
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