数据存储-CoreData geelbank

什么是 CoreData
它不是数据库!
通常用于数据库做为底层存储
也可以使用XML文件;

基本概念

Snip20160427_8.png

创建模型

创建文件,重点吧use Data 打上勾

进入,添加entity

帮entity添加属性

创建HomeWork,添加剂对应属性

创建student,添加剂对应属性

设置关系

因为一个学生对应多个作业, 而不是 一个作业对应多个学生
to many

这里其实推荐做双线链接
可以选这不看表格 ,看关系图

Snip20160427_19.png

你的是不是这样呢?

Snip20160427_20.png

生成文件

Snip20160427_23.png

我们模型建立完毕 ,下面说说环境设置

//
//  ViewController.m
//  HelloCoreData
//
//  Created by zhu on 16/4/27.
//  Copyright © 2016年 zhu. All rights reserved.
//

#import "ViewController.h"
#import "Student.h"
#import "HomeWork.h"
#import "AppDelegate.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
[self setCoreData];

}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}


-(void)setCoreData{
AppDelegate *delegate = [[UIApplication sharedApplication]delegate];
NSManagedObjectContext *context = [delegate managedObjectContext];

Student *personOne = [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:context];
personOne.age = @15;
personOne.name = @"Jack";


HomeWork *HomeWorkOne = [NSEntityDescription insertNewObjectForEntityForName:@"HomeWork" inManagedObjectContext:context];
[HomeWorkOne setValue:@"EnglishHomeWrok" forKey:@"content"];

NSMutableSet *homeworks =[personOne.works mutableCopy];
[homeworks addObject:HomeWorkOne];
[personOne addWorks:homeworks];



UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(0, 100, 2000, 100)];


  //来个大神帮我处理一下.如何便捷提出personOne的科目...
 // label.text=(personOne的科目);
 [self.view addSubview:label];


NSError *error = nil;
if(![context save:&error])
{
    NSLog(@"不能保存：%@",[error localizedDescription]);
}else {
    NSLog(@"新增成功");
}


    //查询
    NSFetchRequest *request = [ NSFetchRequest fetchRequestWithEntityName:@"Student"];
    //排序(过滤名字用J开头的)
    request.sortDescriptors =@[[NSSortDescriptor sortDescriptorWithKey:@"age" ascending:YES]];
    request.predicate = [NSPredicate predicateWithFormat:@"age >%@",@"12"];
//
    //执行
    NSError *requestError= nil;
    NSArray *objs = [context executeFetchRequest:request error:&requestError];
if (requestError) {
    [NSException raise:@"@Qure failed" format:@"%@",[requestError localizedDescription]];
}


[self.view  addSubview:label];
    //遍历结果
    for (_obj in objs) {
        NSLog(@"====================================");
        NSLog(@"name = %@",[_obj valueForKey:@"name"]);
        NSLog(@"age = %@",[_obj valueForKey:@"age"]);
        NSLog(@"works = %@",[_obj valueForKey:@"works"]);
        NSLog(@"====================================");
        
    }



}
@end