###coredata 增删改查

//删除，修改，添加，都需要同步数据

//查询无需同步数据

####coreData插入

 Employee *employee = [NSEntityDescription insertNewObjectForEntityForName:@"Employee" inManagedObjectContext:self.context];  
        employee.name = [NSString stringWithFormat:@"wangwu%u",(unsigned)i];  
    [self.context  save:nil];

####CoreData 查询

//1.1:FectchRequest 抓取请求对象  
    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Employee"];  
    //1.2:设置过滤条件  
    NSPredicate *pre = [NSPredicate predicateWithFormat:@"name = %@",@"张三"];  
    request.predicate = pre;  
    //1.3执行查询请求  
    NSArray *emps = [self.context executeFetchRequest:request error:nil];

####coredata删除

        //1:先查询到需要删除的数据(比如这里以删除员工张三的数据为例)  
        同CoreData 查询
        //2:执行删除操作  
        [self.context deleteObject:emp];  

      //3:保存  
    [self.context save:nil];

####coredata修改

      //1:先查询到需要删除的数据(比如这里以删除员工张三的数据为例)  
        同CoreData 查询
    //2更新数据
            emp.height = @3;  
    //3:保存  
    [self.context save:nil];