CoreData

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封装CoreManager类

@implementation CoreDataManager

{

    //上下文

    NSManagedObjectContext *_ctx;

}

 //单例

+(instancetype)sharedManager

{

    static CoreDataManager *manager = nil;

    static dispatch_once_t onceToken;

    dispatch_once(&onceToken, ^{

        manager = [[CoreDataManager alloc] init];

    });

    return manager;

}

 //初始化时,同事初始化相关的

-(instancetype)init

{

    self = [super init];

    if (self) {

        //初始化上下文对象

        //1.关联实体描述文件(User.xcdatamodeld)

        //扩展名写@“momd”

        NSString *path = [[NSBundle mainBundle] pathForResource:@"GuoFuBao" ofType:@"momd"];

        NSURL *url = [NSURL fileURLWithPath:path];

        NSManagedObjectModel *model = [[NSManagedObjectModel alloc] initWithContentsOfURL:url];       

        //2.关联数据库文件

        NSPersistentStoreCoordinator *coor = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:model];

        //数据库文件的路径

        NSString *dataPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/gfb.sqlite"];

        NSLog(@"path=%@",dataPath);

        NSURL *dataUrl = [NSURL fileURLWithPath:dataPath];

               //CoreData管理的数据库文件升级时传参

        NSDictionary *optionDict = @{NSMigratePersistentStoresAutomaticallyOption:[NSNumber numberWithBool:YES],NSInferMappingModelAutomaticallyOption:[NSNumber numberWithBool:YES]};

        [coor addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:dataUrl options:optionDict error:nil];

        //3.上下文对象

        _ctx = [[NSManagedObjectContext alloc] init];

        _ctx.persistentStoreCoordinator = coor;

    }

    return self;

}

增(插入)

//插入数据
- (IBAction)insertData{
    NSLog(@"插入数据");
    //创建模型数据模型
    Student *student = [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:self.managedContext];
    student.name = @"张三2";
    student.id = @(11);

    Book *book = [NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:self.managedContext];
    book.bookID = @(121);
    book.bookName = @"<老人与海2>";

    student.book = book;

    Student *student2 = [NSEntityDescription insertNewObjectForEntityForName:@"Student" inManagedObjectContext:self.managedContext];
    student2.name = @"李四2";
    student2.id = @(23);

    Book *book2 = [NSEntityDescription insertNewObjectForEntityForName:@"Book" inManagedObjectContext:self.managedContext];
    book2.bookID = @(242);
    book2.bookName = @"<飞鸟集2>";

    student2.book = book2;

    //保存,用 save 方法
    NSError *error = nil;
    BOOL success = [self.managedContext save:&error];
    if (!success) {
        [NSException raise:@"访问数据库错误" format:@"%@",[error localizedDescription]];
    }
}

删(删除)

//删除
- (IBAction)removeData:(id)sender{

    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Student"];

    //查到到你要删除的数据库中的对象
    NSPredicate *predic = [NSPredicate predicateWithFormat:@"name = %@",@"张三2"];
    request.predicate = predic;

    //请求数据
    NSArray *objs = [self.managedContext executeFetchRequest:request error:nil];

    for (Student *stu in objs) {
        [self.managedContext deleteObject:stu];
    }

    [self.managedContext save:nil];
}

查

/读取数据库文件
- (IBAction)readData{
    NSLog(@"读取数据");
    dispatch_async(dispatch_get_main_queue(), ^{

        // 初始化一个查询请求
        //  NSFetchRequest *request = [[NSFetchRequest alloc] init];
        // 设置要查询的实体
        // request.entity = [NSEntityDescription entityForName:@"Student" inManagedObjectContext:self.managedContext];

        //以上代码简写成下边
        NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Student"];

        // 设置排序（按照age降序）
        NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"id" ascending:NO];
        request.sortDescriptors = [NSArray arrayWithObject:sort];
        // 设置条件过滤(搜索name中包含字符串"zhang"的记录，注意：设置条件过滤时，数据库SQL语句中的%要用*来代替，所以%Itcast-1%应该写成*zhang*)
        // NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name like %@", @"*zhang*"];
        // request.predicate = predicate;

        // 执行请求
        NSError *error = nil;
        NSArray *objs = [self.managedContext executeFetchRequest:request error:&error];
        if (error) {
            [NSException raise:@"查询错误" format:@"%@", [error localizedDescription]];
        }

        NSLog(@"-----------------------------------");
        // 遍历数据
        int index = 0;
        for (NSManagedObject *obj in objs) {
            NSLog(@"%d---name=%@", index++,[obj valueForKey:@"name"]);
        }

        for (Student *stu in objs) {
            Book *book = stu.book;
            NSLog(@"%@---name=%@", stu.name,book.bookName);
        }

    });
}

改(更新)

//更新数据
- (IBAction)modifyData{
    // 如果是想做更新操作：只要在更改了实体对象的属性后调用[context save:&error]，就能将更改的数据同步到数据库
    //先从数据库中取出所有的数据,然后从其中选出要修改的那个,进行修改,然后保存


    NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Student"];

    //设置过滤条件
    NSPredicate *pre = [NSPredicate predicateWithFormat:@"name = %@",@"李四2"];
    request.predicate = pre;

    NSError *error = nil;
    NSArray *objs = [self.managedContext executeFetchRequest:request error:&error];
    if (error) {
         [NSException raise:@"查询错误" format:@"%@", [error localizedDescription]];
    }

    // 2.更新身高
    for (Student *stu in objs) {
        stu.name = @"被修改的新名字";
    }

   //保存,用 save 方法
   BOOL success = [self.managedContext save:&error];
   if (!success) {
       [NSException raise:@"访问数据库错误" format:@"%@",[error localizedDescription]];
   }

}

CoreData

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原文地址：http://www.cnblogs.com/daxueshan/p/5850079.html