Core Data demo介绍

 /*CoreData*/

//managedObjectModel的初始化赋值函数

-(NSManagedObjectModel *)managedObjectModel

{

    if (_managedObjectModel != nil) {

        return _managedObjectModel;

    }

    _managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil] ;

    return _managedObjectModel;

}

//持久性存储区

-(NSPersistentStoreCoordinator *)persistentStoreCoordinator

{

    if (_persistentStoreCoordinator != nil) {

       return   _persistentStoreCoordinator;

    }

    //得到数据库的路径

    NSString *docs = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];

    //CoreData是建立在SQLite之上的，数据库名称需与Xcdatamodel文件同名

    NSURL *storeUrl = [NSURL fileURLWithPath:[docs stringByAppendingPathComponent:@"CDJournal.sqlite"]];

    NSError *error = nil;

    _persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc]initWithManagedObjectModel:[self managedObjectModel]];

    if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeUrl options:nil error:&error]) {

        NSLog(@"Error: %@,%@",error,[error userInfo]);

    }

    return _persistentStoreCoordinator;

}

//上下文对象

-(NSManagedObjectContext *)managedObjectContext

{

    if (_managedObjectContext != nil) {

        return _managedObjectContext;

    }

    NSPersistentStoreCoordinator *coordinator =[self persistentStoreCoordinator];

    if (coordinator != nil) {

        _managedObjectContext = [[NSManagedObjectContext alloc]init];

        [_managedObjectContext setPersistentStoreCoordinator:coordinator];

    }

    return _managedObjectContext;

}

//另外，为了保证需要存储的数据不丢失，添加如下代码：这个方法定义的是当应用程序退到后台时将执行的方法，按下home键执行（通知中心来调度）

//实现此方法的目的是将托管对象上下文存储到数据存储区，防止程序退出时有未保存的数据

-(void)applicationWillTerminate:(UIApplication *)application

{

    NSError *error;

    if (_managedObjectContext != nil) {

        //hasChanges方法是检查是否有未保存的上下文更改，如果有，则执行save方法保存上下文

        if ([_managedObjectContext hasChanges] && ![_managedObjectContext save:&error]) {

            NSLog(@"Error: %@,%@",error,[error userInfo]);

            abort();

        }

    }

｝

然后对viewContriller文件进行布局并连接IBOutlet和IBAction

ViewController.h代码如下：

#import <UIKit/UIKit.h>

#import "AppDelegate.h"

@interface ViewController : UIViewController<UITextFieldDelegate>

@property (strong, nonatomic)UITextField *titleTextField;

@property (strong, nonatomic) UITextField *contentTextField;

@property (strong,nonatomic) AppDelegate *myDelegate;

@property (strong,nonatomic) NSMutableArray *entries;

@property (strong,nonatomic)UIButton *addButton;

@property (strong,nonatomic)UIButton *queryButton;

//单击按钮后执行数据保存操作

- (void)addToDB;

//单击按钮后执行查询操作

- (void)queryFromDB;

@end

//

//  ViewController.m

//  CoreDataDemo

//

//  Created by apple on 14/12/15.

//  Copyright (c) 2014年 huweibin. All rights reserved.

//

#import "ViewController.h"

#import "Entity.h"

@interface ViewController ()

@end

@implementation ViewController

- (void)viewDidLoad {

    [super viewDidLoad];

    //获取当前应用程序的委托（UIApplication sharedApplication为整个应用程序上下文）

    self.myDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];

    UILabel * tiitleLabel = [[UILabel alloc]initWithFrame:CGRectMake(20, 100, 80, 50)];

    tiitleLabel.text = @"Tiitle:";

    [self.view addSubview:tiitleLabel];

    self.titleTextField = [[UITextField alloc]initWithFrame:CGRectMake(111,100 ,100 , 50)];

    self.titleTextField.placeholder=@"helloTitile";

    self.titleTextField.delegate= self;

    [self.view addSubview:self.titleTextField];

    UILabel *contentLabel = [[UILabel alloc]initWithFrame:CGRectMake(20, 170,80 , 50)];

    contentLabel.text = @"Content:";

    [self.view addSubview:contentLabel];

    self.contentTextField = [[UITextField alloc]initWithFrame:CGRectMake(111, 170, 100, 50)];

    self.contentTextField.placeholder = @"helloContent";

    self.contentTextField.delegate = self;

    [self.view addSubview:self.contentTextField];

   //单击按钮后执行数据保存操作

    self.addButton = [[UIButton alloc]initWithFrame:CGRectMake(40, 230, 200, 50)];

    [self.addButton setTitle:@"Add" forState:UIControlStateNormal];

    [self.addButton setBackgroundColor:[UIColor grayColor]];

    [self.addButton addTarget:self action:@selector(addToDB) forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:self.addButton];

    //单击按钮后执行查询操作

    self.queryButton = [[UIButton alloc]initWithFrame:CGRectMake(40, 290, 200, 50)];

    [self.queryButton setTitle:@"Query" forState:UIControlStateNormal];

    [self.queryButton setBackgroundColor:[UIColor grayColor]];

    [self.queryButton addTarget:self action:@selector(queryFromDB) forControlEvents:UIControlEventTouchUpInside];

    [self.view addSubview:self.queryButton];

}

- (void)addToDB

{

     //让CoreData在上下文中创建一个新对象(托管对象)

    Entity *entry = (Entity *)[NSEntityDescription insertNewObjectForEntityForName:@"Entity" inManagedObjectContext:self.myDelegate.managedObjectContext];

    [entry setTitle:self.titleTextField.text];

    [entry setBody:self.contentTextField.text];

    [entry setCreationDate:[NSDate date]];

    NSError *error;

    //托管对象准备好后，调用托管对象上下文的save方法将数据写入数据库

    BOOL isSaveSuccess = [self.myDelegate.managedObjectContext save:&error];

    if (!isSaveSuccess) {

        NSLog(@"Error: %@,%@",error,[error userInfo]);

    }else {

        NSLog(@"Save successful!");

    }

}

//单击按钮后执行查询操作

- (void)queryFromDB

{

     //创建取回数据请求

    NSFetchRequest *request = [[NSFetchRequest alloc]init];

    //设置要检索哪种类型的实体对象

    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Entity" inManagedObjectContext:self.myDelegate.managedObjectContext];

    //设置请求实体

    [request setEntity:entity];

    //指定对结果的排序方式

    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"creationDate"ascending:NO];

    NSArray *sortDescriptions = [[NSArray alloc]initWithObjects:sortDescriptor, nil];

    [request setSortDescriptors:sortDescriptions];

    NSError *error = nil;

    //执行获取数据请求，返回数组

    NSMutableArray *mutableFetchResult = [[self.myDelegate.managedObjectContext executeFetchRequest:request error:&error] mutableCopy];

    if (mutableFetchResult == nil) {

        NSLog(@"Error: %@,%@",error,[error userInfo]);

    }

    self.entries = mutableFetchResult;

    NSLog(@"The count of entry:%i",[self.entries count]);

    for (Entity *entry in self.entries) {

        NSLog(@"Title:%@与Content:%@---Date:%@",entry.title,entry.body,entry.creationDate);

    }

}

//更新操作

-(void)updateEntry:(Entity *)entry

{

    [entry setTitle:self.titleTextField.text];

    [entry setBody:self.contentTextField.text];

    [entry setCreationDate:[NSDate date]];

    NSError *error;

    BOOL isUpdateSuccess = [self.myDelegate.managedObjectContext save:&error ];

    if (!isUpdateSuccess) {

        NSLog(@"Error:%@,%@",error,[error userInfo]);

    }

}

//删除操作

-(void)deleteEntry:(Entity *)entry

{

    [self.myDelegate.managedObjectContext deleteObject:entry];

    [self.entries removeObject:entry];

    NSError *error;

    if (![self.myDelegate.managedObjectContext save:&error]) {

        NSLog(@"Error:%@,%@",error,[error userInfo]);

    }

}

//当通过键盘在UITextField中输入完毕后，点击屏幕空白区域关闭键盘的操作

- (BOOL)textFieldShouldReturn:(UITextField *)textField {

    [textField resignFirstResponder];

    return YES;

}

@end