如何防止在分析时重复输入？

Question

我正在尝试保存要分析的歌曲信息，但是如果该歌曲已经存在于分析中，我希望我的代码什么也不做。

我在下面尝试过此代码：

var Music = PFObject(className:"Musics")
        var query = PFQuery(className:"Musics")
        query.findObjectsInBackgroundWithBlock {
            (objects: [AnyObject]?, error: NSError?) -> Void in

            if error == nil {
                // The find succeeded.
                println("Successfully retrieved \(objects!.count) scores.")
                // Do something with the found objects
                if let objects = objects as? [PFObject] {
                    for object in objects {


                        var songTitle = object.objectForKey("songTitle") as? String

                        if songTitle != title {

                            Music["createdBy"] = PFUser.currentUser()
                            Music["songTitle"] = title
                            Music["albumCover"] = imageFile
                            Music["songArtist"] = artist
                            Music.saveInBackgroundWithBlock {

                                (success: Bool, error: NSError?) -> Void in
                                if (success) {

                                    println("succeed")

                                } else {
                                    // There was a problem, check error.description
                                    println("error jeh")
                                }
                            }

                        }else{

                            println("song already exist")

                        }

                    }
                }
            } else {
                // Log details of the failure
                println("Error: \(error!) \(error!.userInfo!)")
            }
        }

上面的代码在日志中给出以下结果：

成功取得4分。歌曲已存在成功检索到4个乐谱。歌曲已存在成功检索到4个乐谱。歌曲已存在成功检索到4个乐谱。歌曲已存在成功成功成功成功成功成功成功成功成功成功成功成功

为什么我的for循环比Objects.count循环更多？以及如何防止解析中出现重复项？

给我任何建议，在obj c或swift中都没关系

Answer 1

我建议在Parse Cloud代码上实现一个简单的beforeSave触发器，以检查新的输入歌曲是否已经存在（基本上，您将使一个或多个字段唯一。例如：

Parse.Cloud.beforeSave("Musics", function(request, response) {

  var newEntrySong = request.object;

  var querySongs = new Parse.Query("Musics");
  querySongs.equalTo("title", newEntrySong.get("title"));
  querySongs.equalTo("description", newEntrySong.get("description"));

  // this could be a sort of signature for your song, to make more unique (skipping spaces and new lines for example)
  querySongs.equalTo("md5Title", newEntrySong.get("md5Title"));
  querySongs.first({
    success: function(temp) {
        response.error({errorCode:123,errorMsg:"Song already exist!"});          
    },
    error: function(error) {
      response.success();
    }
  });
});

希望能帮助到你。