使用CoreData [1]

本篇教程能教你从无开始接触CoreData,包括新建工程,创建出实体,增删改查样样都有,属于使用CoreData最初级教程.

1. 创建带有CoreData的工程项目

2. 添加一个实体类

3. 创建出实体类

4. 创建对象,保存对象,执行代码

以下是验证结果:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    NSLog(@"%@", NSHomeDirectory());

    // 实体描述信息

    NSEntityDescription *description = \

        [NSEntityDescription entityForName:@"Student"

                    inManagedObjectContext:[self managedObjectContext]];

    // 初始化对象

    Student *student = [[Student alloc] initWithEntity:description

                        insertIntoManagedObjectContext:[self managedObjectContext]];

    student.name     = @"YouXianMing";

    student.age      = [NSNumber numberWithInt:];

    // 保存对象

    [self saveContext];

    return YES;

}

这样就实现了存储对象.

5. 重复上面的步骤存储5个对象.

6. 遍历出所有的对象

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    // 设定要查询的实体

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

    // 取出查询结果

    NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];

    // 遍历

    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        Student *student = obj;

        NSLog(@"%@ %@", student.age, student.name);

    }];

    return YES;

}

7. 删除一个对象

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    // 设定要查询的实体

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

    // 取出查询结果

    NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];

    // 遍历

    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        Student *student = obj;

        // 找到匹配的数据,删除之

        if ([student.name isEqualToString:@"QiuLiang"])

        {

            [[self managedObjectContext] deleteObject:student];

        }

    }];

    // 存储

    [self saveContext];

    // 遍历

    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        Student *student = obj;

        NSLog(@"%@ %@", student.age, student.name);

    }];

    return YES;

}

8. 修改一个对象

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

{

    // 设定要查询的实体

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

    // 取出查询结果

    NSArray *students = [[self managedObjectContext] executeFetchRequest:fetch error:nil];

    // 遍历

    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        Student *student = obj;

        // 找到匹配的数据,修改之

        if ([student.name isEqualToString:@"YouXianMing"])

        {

            student.age = [NSNumber numberWithInt:];

        }

    }];

    // 存储

    [self saveContext];

    // 遍历

    [students enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {

        Student *student = obj;

        NSLog(@"%@ %@", student.age, student.name);

    }];

    return YES;

}

9. 根据谓词查找出实体的方法请自行百度脑补,这里不赘述了.

巴特西

使用CoreData [1]

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