CoreData

参考了前辈的作品:http://blog.csdn.net/kesalin/article/details/6739319

 

1.ManagedObjectModel  :

描述应用程序的数据模型 包含了实体(Entity) 属性(Property) 读取数据的等

//xcdataModeld文件编译后为momd文件 从资源文件中加载NSManagedObjectModel对象
    NSURL *url = [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"];
    _model = [[NSManagedObjectModel alloc] initWithContentsOfURL:url];

 

2.ManagedObjectContext:

ManagedObjectContext 参与对数据操作的全过程 并检测数据对象的变化  下面的代码可看出到处都有 他的影子

    //通过NSManagedObjectModel对象创建NSPersistentStoreCoordinator对象
    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:_model];
////数据库的增删改查
//插入
- (void)insertWithName:(NSString *)name
{
    People *people = [NSEntityDescription insertNewObjectForEntityForName:ENTITY_NAME inManagedObjectContext:_context];
    people.name = name;
    //baocunxiugai
    NSError *error = nil;
    if (![_context save:&error])
    {
        NSLog(@"插入数据失败");
    }
}
//检索所有
- (NSArray *)searchAll
{
    NSFetchRequest *req = [NSFetchRequest fetchRequestWithEntityName:ENTITY_NAME];
    NSArray *resultArr = [_context executeFetchRequest:req error:nil];
    return resultArr;
    
}
//更新对象
- (void)updateWithPeople:(People *)people
{
    NSError *error = nil;
    if (![_context save:&error])
    {
        NSLog(@"Update fail");
    }
}
//删除数据
- (void)deletePeople:(People *)people
{
    [_context deleteObject:people];
    
    NSError *error = nil;
    if (![_context save:&error])
    {
        NSLog(@"Delete fail");
    }
}

3.PersistentStoreCoordinator:

PersistentStoreCoordinator相当于数据文件管理器 处理底层对数据文件的读取与写入  

 //文件夹路径
    NSString *path = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"Model.sqlite"];
    //加载文件
    if ([_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:[NSURL fileURLWithPath:path] options:nil error:nil])
    {
        _context = [[NSManagedObjectContext alloc] init];
        //为NSManagedObjectContext对象设置存储协调者
        [_context setPersistentStoreCoordinator:_persistentStoreCoordinator];
    }
    else
    {//加载出错 就崩溃
        abort();
    }

4.ManagedObject

数据对象 与ManagedObjectContext相关联