javascript - 云代码上的 promise

Question

我正在编写一个云代码函数，用于在删除对象后运行许多任务。我怎样才能干净地做到这一点并且不嵌套？

您可以并行运行任务，还是按顺序运行任务更好？如果是这样，怎么办？

这是我的代码，你能帮我清理/更改吗？

Parse.Cloud.afterDelete("Photo", function(request) {
  Parse.Cloud.useMasterKey();
  //delete all related activities
  var queryAct = new Parse.Query("Activity");
  queryAct.equalTo("photo",{
    __type: "Pointer",
    className: "Photo",
    objectId: request.object.id
  });
  queryAct.limit(1000);
  queryAct.find({
    success: function(activities) {
      Parse.Object.destroyAll(activities, {
        success: function() {
          //delete all related hashtags
          var queryTags = new Parse.Query("hashTags");
          queryTags.equalTo("photo",{
            __type: "Pointer",
            className: "Photo",
            objectId: request.object.id
          });
          queryTags.limit(1000);
          queryTags.find({
            success: function(hashtags) {
              Parse.Object.destroyAll(hashtags, {
                success: function() {},
                 error: function(error) {
                  console.error("Error deleting related hashtags " + error.code + ": " + error.message);
                }
              });
            },
            error: function(error){
              console.error("Error finding related hashtags " + error.code + ": " + error.message); 
            }
          });
        },
        error: function(error) {
          console.error("Error deleting related activities " + error.code + ": " + error.message);
        }
      });
    },
    error: function(error) {
      console.error("Error finding related activities " + error.code + ": " + error.message);
    }
  });
});

谢谢大家!

Answer 1

这里find.then.delete是一系列连续的任务。不过，您可以同时删除hastags 和activities，因为它们似乎并不相关。请查看promises guide了解更多信息。您的代码可以缩短如下:

var Photo = Parse.Object.extend("Photo");

Parse.Cloud.afterDelete("Photo", function(request) {
  Parse.Cloud.useMasterKey();

  var photo = Photo.createWithoutData(request.object.id);

  var queryAct = new Parse.Query("Activity");
  queryAct.equalTo("photo", photo);
  queryAct.limit(1000);
  var promiseForActivities = queryAct.find().then(function (activities) {
    return Parse.Object.destroyAll(activities);
  });

  var queryTags = new Parse.Query("hashTags");
  queryTags.equalTo("photo", photo);
  queryTags.limit(1000);
  var promiseForHashtags = queryTags.find().then(function (hashtags) {
    return Parse.Object.destroyAll(hashtags);
  });

  return Parse.Promise.when([promiseForActivities, promiseForHashtags]).then(function () {
    console.log("Done");
  }, function (err) {
    console.error(err);
  });
});

请注意，您不需要创建自己的指针对象，例如:

{
  __type: "Pointer",
  className: "Photo",
  objectId: "someId"
}

您可以使用 createWithoutData这是以下内容的快捷方式:

var Photo = Parse.Object.extend("Photo");
var p = new Photo();
p.id = "someId";

我还认为直接传递 request.object 就足够了，例如 queryAct.equalTo("photo", request.object);