CoreData周り

CoreDataTest.m

/*
 * save
 */
-(void)save{
    NSError *error = nil;
    if (![[self managedObjectContext] commitEditing]) {
        NSLog(@"%@:%@ unable to commit editing before saving", [self class], NSStringFromSelector(_cmd));
    }
    if (![[self managedObjectContext] save:&error]) {
        [[NSApplication sharedApplication] presentError:error];
    }
}

/*
 * insert
 */
 // NSManagedObjectの生成
-(NSManagedObject*)createObject:(NSString*)entity_name{
    return [NSEntityDescription insertNewObjectForEntityForName:entity_name inManagedObjectContext:self.managedObjectContext];
}
// insertの実行
-(void)insert{
     // NSManagedObjectの生成
    TaskSource *taskSource = (TaskSource*)[self createObject:@"TaskSource"];
    taskSource.task_name = @"task1";
    taskSource.interval = [[NSNumber alloc]initWithInt:10];
    // Relationがある場合、対象レコードを取得
    NSFetchRequest *request = [self createRequest:@"Notebook"];
    NSError *error = nil;
    NSArray *result = [self.managedObjectContext executeFetchRequest:request error:&error];
    Notebook *notebook = [result objectAtIndex:0];
    taskSource.notebook = notebook;
    [self save];
}    

/*
 * select
 */
 // fetchRequestの生成
-(NSFetchRequest*)createRequest:(NSString*)entity_name{
    return [[NSFetchRequest alloc] initWithEntityName:entity_name];
}
// 検索
-(void)select{
    // 全件検索
    NSFetchRequest *fetchRequest = [self createRequest:@"ENTITY_NAME"];
    NSError *error = nil;
    NSArray *result = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];
    for(TaskSource *taskSource in result) {
        [taskSource print];
    }

    // 以下、各種条件は設定後にexecuteFetchRequestを実施
    // ソート条件の設定
    NSSortDescriptor *desc;
    desc = [[NSSortDescriptor alloc] initWithKey:@"interval" ascending:NO];
    NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:desc, nil];
    [fetchRequest setSortDescriptors:sortDescriptors];

    // 取得条件の設定
   NSPredicate *pred = [NSPredicate predicateWithFormat:@"task_name = %@", @"task1"];  // 1:key, 2:value
   [fetchRequest setPredicate:pred];
    
    // 取得最大数の設定
    [fetchRequest setFetchBatchSize:10];
    [fetchRequest setFetchLimit:1];    // 取得最大数

}

// 集計関数検索 : select task_name, sum(interval) from task_source group by task_name;
-(void)select_groupby{
    // fetchRequestの生成
    NSFetchRequest *fetchRequest = [self createRequest:@"ENTITY_NAME"];

    //集計の対象を設定します。
    NSExpression *keyPathExpression = [NSExpression expressionForKeyPath:@"interval"];  

    //集計関数(sum)の指定
    NSExpression *expression = [NSExpression expressionForFunction:@"sum:" arguments:[NSArray arrayWithObject:keyPathExpression]];    

    //集計式の対象（NSExpressionDescription ）
    NSExpressionDescription *expressionDescription = [[NSExpressionDescription alloc] init];
    [expressionDescription setName:@"sumInterval"]; //集計式の名
    [expressionDescription setExpression:expression]; //集計関数
    [expressionDescription setExpressionResultType:NSInteger32AttributeType]; //結果の種類    
    [request setPropertiesToGroupBy:[NSArray arrayWithObject:@"task_name"]];    // gourybyのkey
    [request setPropertiesToFetch:[NSArray arrayWithObjects: expressionDescription, @"task_name", Nil]];    // 出力カラム(group by key)
    [request setResultType:NSDictionaryResultType];
    
    //結果を取得
    NSArray *objs= [self.managedObjectContext executeFetchRequest:request error:nil];
    for(int i=0; i < objs.count; i++){
        NSArray *array = [objs objectAtIndex:i];
        NSLog(@"%@:%@", [array valueForKey:@"task_name"], [array valueForKey:@"sumInterval"]);
    }
}