勾选 xcode的 CoreDate会帮我们自动创建 CoreData 但是我们通常不那样使用,通常把 CoreDate 在单例类中创建

//
//  ZYDAO.h
//  StoryboardTest
//
//  Created by ninglihuan on 15/11/27.
//  Copyright © 2015年 zzz. All rights reserved.
//

#import <Foundation/Foundation.h>
#import "People.h"

@interface ZYDAO : NSObject

+ (instancetype)sharedDAO;

- (People* )insertPeopleWithName:(NSString* )name phone:(NSString* )phone;

- (NSArray* )selectAllPeople;

- (void)updatePeople;

- (void)deletePeople:(People* )people;

@end

//
//  ZYDAO.m
//  StoryboardTest
//
//  Created by ninglihuan on 15/11/27.
//  Copyright © 2015年 zzz. All rights reserved.
//

#import "ZYDAO.h"
@import CoreData;

NSString* const PEOPLE = @"People";

@interface ZYDAO () {
    NSManagedObjectModel* _model;
    NSPersistentStoreCoordinator* _coordinator;
    NSManagedObjectContext* _context;
}

@end

@implementation ZYDAO

+ (instancetype)sharedDAO {
    static ZYDAO* dao = nil;
    
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        dao = [[ZYDAO alloc] init];
    });
    
    return dao;
}

- (id)init {
    if (self = [super init]) {
        NSURL* modelURL = [[NSBundle mainBundle] URLForResource:@"Model" withExtension:@"momd"];
        
        _model = [[NSManagedObjectModel alloc] initWithContentsOfURL:modelURL];
        
        _coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:_model];
        
        NSURL* sqliteURL = [[[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] lastObject] URLByAppendingPathComponent:@"Model.sqlite"];
        
        if (![_coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:sqliteURL options:nil error:nil]) {
            NSLog(@"打开数据库失败");
        }
        
        _context = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSMainQueueConcurrencyType];
        
        [_context setPersistentStoreCoordinator:_coordinator];
    }
    
    return self;
}

- (People* )insertPeopleWithName:(NSString* )name phone:(NSString* )phone {
    People* people = [NSEntityDescription insertNewObjectForEntityForName:PEOPLE inManagedObjectContext:_context];

    people.name = name;
    people.phone = phone;
    
    //把修改同步到数据库。
    [_context save:nil];
    
    return people;
}

- (NSArray* )selectAllPeople {
    NSFetchRequest* request = [NSFetchRequest fetchRequestWithEntityName:PEOPLE];
    
    return [_context executeFetchRequest:request error:nil];
}

- (void)updatePeople {
    [_context save:nil];
}

- (void)deletePeople:(People* )people {
    [_context deleteObject:people];
    
    [_context save:nil];
}

@end