Parse.comで特定のchannelを削除したい場合

Parse便利だけど、channelの操作は自分でやんないとだめっぽい。
addChannel / removeChannel ってメソッド作って対処。

-(void)addChannel:(NSString*)str
{
    if(![[PFInstallation currentInstallation].channels containsObject:str])
    {
        NSMutableArray *channels = [[PFInstallation currentInstallation].channels mutableCopy];
        [channels addObject:str];
        [PFInstallation currentInstallation].channels = channels;
        [[PFInstallation currentInstallation] saveInBackground];
    }
}

-(void)removeChannel:(NSString*)str
{
    if([[PFInstallation currentInstallation].channels containsObject:str])
    {
        NSMutableArray *channels = [[PFInstallation currentInstallation].channels mutableCopy];
        [channels removeObject:str];
        [PFInstallation currentInstallation].channels = channels;
        [[PFInstallation currentInstallation] saveInBackground];
    }
}