[数据存储之七]CoreData操作练习

柔情只为你懂 2022-07-28 01:47 132阅读 0赞

算是第一个功能全面些的例子吧，实现了利用CoreData的添加，删除，修改，查询的操作。

功能简单，CoreData提供的东西也没仔细看。关键代码贴上：

添加和修改代码：

NSData* iconData = UIImageJPEGRepresentation(_ImgViewCurrent.image, 1.0);
        if (self.OpenViewModal == vmAddNew) {
            NSManagedObject* Record = [NSEntityDescription insertNewObjectForEntityForName:@"Students"
                                                                    inManagedObjectContext:_DBContext];
            [Record setValue:_TextFiledName.text forKey:cdbName];
            [Record setValue:_TextFiledPhone.text forKey:cdbTelephone];
            [Record setValue:[NSNumber numberWithBool:_SwitchSex.on] forKey:cdbSex];
            [Record setValue:iconData forKey:cdbIcon];
        }
        else{
            [self.EditReord setValue:_TextFiledName.text forKey:cdbName];
            [self.EditReord setValue:_TextFiledName.text forKey:cdbName];
            [self.EditReord setValue:_TextFiledPhone.text forKey:cdbTelephone];
            [self.EditReord setValue:[NSNumber numberWithBool:_SwitchSex.on] forKey:cdbSex];
            [self.EditReord setValue:iconData forKey:cdbIcon];
        }
        [_DBContext save:nil];
        [PublicFuns ShowMsg:@"保存完成!"];
        [self.navigationController popViewControllerAnimated:YES];

查询代码：

-(void)RefreshData
    {
        AppDelegate* delegate = [UIApplication sharedApplication].delegate;
        NSManagedObjectContext* _context = delegate.managedObjectContext;
        NSFetchRequest* Requst = [[NSFetchRequest alloc] initWithEntityName:@"Students"];
        NSEntityDescription* Entity = [NSEntityDescription entityForName:@"Students"
                                                  inManagedObjectContext:_context];
        [Requst setEntity:Entity];
        _FethchsObjects = [NSMutableArray arrayWithArray:[_context executeFetchRequest:Requst error:nil]];
        [self.tableView reloadData];
    }

NSManagedObject* Record = _FethchsObjects[indexPath.row];
        UITableViewCell* Cell = nil;
        if ([[Record valueForKey:cdbSex] boolValue]) {
            Cell = [tableView dequeueReusableCellWithIdentifier:@"man"];
        }
        else {
            Cell = [tableView dequeueReusableCellWithIdentifier:@"woman"];
        }
        [Cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator];
        _DoubleGesture=[[UITapGestureRecognizer alloc] initWithTarget:self
                                                               action:@selector(EditStudent)];
        [_DoubleGesture setNumberOfTapsRequired:2];
        [Cell addGestureRecognizer:_DoubleGesture];
        UIImageView* ImgView = (UIImageView*)[Cell viewWithTag:1];
        UILabel* LabName = (UILabel*)[Cell viewWithTag:2];
        UILabel* LabPhone = (UILabel*)[Cell viewWithTag:3];
        NSData* iconData = (NSData*)[Record valueForKey:cdbIcon];
        ImgView.image = [UIImage imageWithData:iconData];
        LabName.text = [Record valueForKey:cdbName];
        LabPhone.text = [Record valueForKey:cdbTelephone];
        return Cell;

删除代码：

-(void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath
    {
        NSInteger row = [indexPath row];
        if (editingStyle == UITableViewCellEditingStyleDelete) {
            AppDelegate* delegate = [UIApplication sharedApplication].delegate;
            NSManagedObjectContext* _context = delegate.managedObjectContext;
            [_context deleteObject:_CurrentObject];
            [_FethchsObjects removeObject:_CurrentObject];
            [_context save:nil];
            NSArray* DelArr = [NSArray arrayWithObject:[NSIndexPath indexPathForRow:row inSection:0]];
            [tableView deleteRowsAtIndexPaths:DelArr
                             withRowAnimation:UITableViewRowAnimationBottom];
            [PublicFuns ShowMsg:@"删除完成!"];
        }
    }

总结下吧：

1，实现了利用CoreData，存储数据，例子中包括字符串,BOOL,二进制类型的数据。

2，操练了利用stroyBoard实现水平等分的方法，这个开始研究的时候，挺费时间的。

3，利用了oc的performSelector:WithObject的概念，给对象发送消息，降低耦合。但arc环境处理费点儿事，下面是两种处理方式。

-(void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
    {
        id EditController = segue.destinationViewController;
        
        /*大师级写法啊～*/
        SEL SelModal = NSSelectorFromString(@"setOpenViewModal:");
        IMP impModal = [EditController methodForSelector:SelModal];
        void(*FuncModal)(id,SEL,NSInteger) = (void*) impModal;
        FuncModal(EditController,SelModal,[sender integerValue]);
        
        /*SEL SelRecord = NSSelectorFromString(@"setEditReord:");
        IMP impRcord = [EditController methodForSelector:SelRecord];
        void(*FuncRecord)(id,SEL,id) = (void*) impRcord;
        FuncRecord(EditController,SelModal,_CurrentObject);*/
        /*推荐方式啊，一劳永逸～*/
        SuppressPerformSelectorLeakWarning
        (
          SEL SelRecord = NSSelectorFromString(@"setEditReord:");
          [EditController performSelector:SelRecord withObject:_CurrentObject];
         );
    
    }

宏的原型：

#define SuppressPerformSelectorLeakWarning(Stuff) \
    do { \
    _Pragma("clang diagnostic push") \
    _Pragma("clang diagnostic ignored \"-Warc-performSelector-leaks\"") \
    Stuff; \
    _Pragma("clang diagnostic pop") \
    } while (0)

上个图吧：

![Center][]

[Center]: /images/20220727/49f8e3eb37974400aec0451a5055f15e.png