Core Data 简单入门

1.在.xcdatamodeld中添加实体

2.添加相应实体类

 

 

3.导入（coredata.framework 在开始时已选择use core data 自动添加）

 

4.初始化响应信息

 // 从应用程序包中加载模型文件
    NSManagedObjectModel *model = [NSManagedObjectModel mergedModelFromBundles:nil];
    
    //初始化持久化对象
    NSPersistentStoreCoordinator *per=[[NSPersistentStoreCoordinator alloc]initWithManagedObjectModel:model];
    
    //创建sqlight路径
    NSString *path=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) firstObject];
    NSURL *url=[NSURL fileURLWithPath:[path stringByAppendingPathComponent:@"person.data"]];
    
    //添加持久化存储
    NSError *error=nil;
   NSPersistentStore *store = [per addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:url options:nil error:&error];
    
    if (store == nil) { // 直接抛异常
        [NSException raise:@"添加数据库错误" format:@"%@", [error localizedDescription]];
        
        NSLog(@"打开数据库失败！---%@",error.localizedDescription);
        
    }else{
        
        NSLog(@"打开数据库成功！");
        
        // 初始化上下文，设置persistentStoreCoordinator属性
        self.context = [[NSManagedObjectContext alloc] init];
        _context.persistentStoreCoordinator = per;
    }

现在就可以根据上下文context进行增删改查操作了

 

 

5.添加数据

  //传入上下文，初始化一个person
//    NSManagedObject *person=[NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.context];
//    [person setValue:@"张三" forKeyPath:@"name"];
//    [person setValue:[NSNumber numberWithInt:25] forKeyPath:@"age"];
//    
//    //初始化card
//    NSManagedObject *card=[NSEntityDescription insertNewObjectForEntityForName:@"Card" inManagedObjectContext:self.context];
//    [card setValue:@"1234567" forKeyPath:@"no"];
//    
//    //创建card和person关系
//    [person setValue:card forKeyPath:@"Card"];
    
    // 2）model方式
    Person *person=[NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:self.context];
    person.name=@"张三";
    person.age=[NSNumber numberWithInt:25];
    
    Card *card=[NSEntityDescription insertNewObjectForEntityForName:@"Card" inManagedObjectContext:self.context];
    card.no=@"123456";
    
    person.card=card;
    
    //利用上下文保存数据
    NSError *error=nil;
    
    BOOL result=[self.context save:&error];
    
    if (result) {
        NSLog(@"插入成功");
    }else{
        NSLog(@"插入失败");
    }

 

6.查询数据

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:self.context];
    [fetchRequest setEntity:entity];
    
    // 设置条件过滤时，数据库SQL语句中的%要用*来代替
//    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name like %@", @"张"];
//    [fetchRequest setPredicate:predicate];
    
    // 排序
    NSSortDescriptor *sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"age"
                                                                   ascending:YES];
    [fetchRequest setSortDescriptors:[NSArray arrayWithObjects:sortDescriptor, nil]];
    
    NSError *error = nil;
    NSArray *fetchedObjects = [self.context executeFetchRequest:fetchRequest error:&error];
    if (fetchedObjects == nil) {
        NSLog(@"查询失败");
    }else
    {
        for (Person *obj in fetchedObjects) {
            Card *car=(Card *)(obj.card);
            NSLog(@"name:%@",car.no);
        }
    }

 

7.删除数据

 NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Person" inManagedObjectContext:self.context];
    [fetchRequest setEntity:entity];
    
    
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age=%@", [NSNumber numberWithInt:25]];
    [fetchRequest setPredicate:predicate];
    
    NSError *error = nil;
    NSArray *fetchedObjects = [self.context executeFetchRequest:fetchRequest error:&error];
    if (fetchedObjects != nil) {
        for (Person *obj in fetchedObjects) {
            [self.context deleteObject:obj];
        }
        
        NSError *error=nil;
        [self.context save:&error];
        if (error) {
            NSLog(@"删除错误");
        }else {
            NSLog(@"删除成功");
        }
    }