CoreData数据库操作

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CoreData增删改查

messageFetchRequest.predicate = [NSPredicate predicateWithFormat:@"toAccount == '130000011111'"];

1.增加一条数据

    NSEntityDescription *enity = [NSEntityDescription entityForName:@"Contact" inManagedObjectContext:self.managedObjectContext];
    Contact *oneContact = [[Contact alloc]initWithEntity:enity insertIntoManagedObjectContext:self.managedObjectContext];
    oneContact.iid = [NSString stringWithFormat:@"%lu", (unsigned long)containsContact.count];
    oneContact.account = realUserName;
    oneContact.status = [[item attributeForName:@"subscription"]stringValue];
    [self.managedObjectContext save:nil];

2.删除一条数据

//不推荐使用谓词,有的时候并不能精确度的找到

    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Contact"];
//    request.predicate = [NSPredicate predicateWithFormat:@"account = '%@'",shieldUsername];
    NSArray *datas = [self.managedObjectContext executeFetchRequest:request error:nil];
    for (Contact *model in datas) {
        if ([model.account isEqualToString:shieldUsername]) {
            [self.managedObjectContext deleteObject:model];
            NSLog(@"删除成功");
        }
    }
    if ([self.managedObjectContext save:nil]) {
        NSLog(@"保存成功");
    }
    else
    {
        NSLog(@"删除失败");
    }

3.修改一条数据,先查后改

        UITextField *textF = alert.textFields.firstObject;
        NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Contact"];
        fetchRequest.predicate = [NSPredicate predicateWithFormat:@"account == %@",self.contactModel.account];
        NSArray *result = [self.managedObjectContext executeFetchRequest:fetchRequest error:nil]; //_managedObjectContext
        for (Contact *model in result) {
            model.name = textF.text;
            _contactModel = model;
            [self.tableView reloadData];
        }
        [_managedObjectContext save:nil];

或

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"RecentSession"];
        request.predicate = [NSPredicate predicateWithFormat:@"fromNumber == %@",weakSelf.contactModel.account];
        NSArray *arr = [weakSelf.managedObjectContext executeFetchRequest:request error:nil];
        RecentSession *recentModel = arr.firstObject;
        if (arr.count != 0) {
            recentModel.fromName = textF.text;
        }
        [weakSelf.managedObjectContext save:nil];

4.全表查询

NSFetchRequest *fetchRequest = [NSFetchRequest fetchRequestWithEntityName:@"Contact"];

    NSArray *containsContact = [self.managedObjectContext executeFetchRequest:fetchRequest error:nil];
    for (Contact *obj in containsContact) {
        if ([obj.account isEqualToString:realUserName]) {
            return;
        }

5.条件查询

                NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Pre_Message"];
                request.predicate = [NSPredicate predicateWithFormat:@"other_msg_id == %@",msgID]; //注意此处@"other_msg_id == %@"
                NSArray *arr = [self.managedobjectContext executeFetchRequest:request error:nil];

6.谓词的使用

-(void)sendFailMessage
{
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]initWithEntityName:@"Pre_Message"];
    fetchRequest.predicate = [NSPredicate predicateWithFormat:@"msgFrom == 'me' and myAccount == %@ and msgType = '0' and msgStatus == 'f' or msgStatus == %@",[[NSUserDefaults standardUserDefaults] objectForKey:@"userPhone"],@""];
    NSArray *arr = [self.objectContext executeFetchRequest:fetchRequest error:nil];
    if (arr.count > 0) {
        NSArray *orderArray = [self orderedTimeWithArray:arr];
        for (Pre_Message *model in orderArray) {
            [[XmppMessageSenderHelper shareSendMessageHelper] sendMessageToJid:[NSString stringWithFormat:@"%@@casing.com",model.toAccount] type:model.msgType context:model.msg1 msgId:model.iid sizelong:nil];
            if ([orderArray indexOfObject:model] >= 100) {
                break;
            }
        }
    }

}

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