Question

我对流星很新，我遇到了订阅回调的奇怪问题。我有一个包含课程和评论的数据库。我在评论中使用发布/订阅模型来返回仅与所选类相关的评论，并且我希望每次单击新类时都要更改。我想打印所有评论并编制一些关于评论的指标（平均质量，难度等级）。使用以下代码，使用订阅更新发送给客户端的评论，打印的评论（从帮助程序中获取）正确返回，但指标（在onReady回调到辅助程序时抓取）是不准确的。运行onReady函数时，本地评论集合的当前结果包含单击的类和先前单击的类的并集，即使评论本身打印正确。

我也试过使用autoTracker，但我得到了相同的结果。有没有办法在更新之前清除以前的订阅结果？

发布：

＆＃13;

Meteor.publish('reviews', function validReviews(courseId, visiblity) {
	  	console.log(courseId);
	  	console.log(visiblity);
	  	var ret = null
	  	//show valid reviews for this course
	  	if (courseId != undefined && courseId != "" && visiblity == 1) {
	  		console.log("checked reviews for a class");
	  		ret =  Reviews.find({class : courseId, visible : 1}, {limit: 700});
	  	} else if (courseId != undefined && courseId != "" && visiblity == 0) { //invalidated reviews for a class
	  		console.log("unchecked reviews for a class");
	  		ret =  Reviews.find({class : courseId, visible : 0},  
			{limit: 700});
	  	} else if (visiblity == 0) { //all invalidated reviews
	  		console.log("all unchecked reviews");
	  		ret =  Reviews.find({visible : 0}, {limit: 700});
	  	} else { //no reviews 
	  		console.log("no reviews");
	  		//will always be empty because visible is 0 or 1. allows meteor to still send the ready 
	  		//flag when a new publication is sent
	  		ret = Reviews.find({visible : 10}); 
	  	}
	  	//console.log(ret.fetch())
	  	return ret
  	});

＆＃13;

this.helpers({
      reviews() {
        return Reviews.find({});
      }        
    });

＆＃13;

并使用帮助程序在构造函数中订阅调用：

＆＃13;

constructor($scope) {
    $scope.viewModel(this);

    //when a new class is selected, update the reviews that are returned by the database and update the gauges
    this.subscribe('reviews', () => [(this.getReactively('selectedClass'))._id, 1], {
      //callback function, should only run once the reveiws collection updates, BUT ISNT 
      //seems to be combining the previously clicked class's reviews into the collection
      onReady: function() {
        console.log("class is: ", this.selectedClass);
        if (this.isClassSelected == true) { //will later need to check that the side window is open
          //create initial variables
          var countGrade = 0;
          var countDiff = 0;
          var countQual = 0;
          var count = 0;

          //table to translate grades from numerical value
          var gradeTranslation = ["C-", "C", "C+", "B-", "B", "B-", "A-", "A", "A+"];

          //get all current reviews, which will now have only this class's reviews because of the subscribe.
          var allReviews = Reviews.find({});
          console.log(allReviews.fetch()); 
          console.log("len is " + allReviews.fetch().length)
          if (allReviews.fetch().length != 0) {
            console.log("exist")
            allReviews.forEach(function(review) {
              count++;
              countGrade = countGrade + Number(review["grade"]);
              countDiff = countDiff + review["difficulty"];
              countQual = countQual + review["quality"];
            });

            this.qual = (countQual/count).toFixed(1);
            this.diff = (countDiff/count).toFixed(1);
            this.grade = gradeTranslation[Math.floor(countGrade/count) - 1];
          } else {
            console.log("first else");
            this.qual = 0;
            this.diff = 0;
            this.grade = "-";
          }
        } else {
          console.log("second else");
            this.qual = 0;
            this.diff = 0;
            this.grade = "-";
        } 
      } 
    })

＆＃13;

Answer 1

当使用pub-sub时，客户端上的minimongo数据库将包含订阅的并集，除非它们被明确清除。因此，您希望在客户端重复发布中的查询，以便以相同的方式进行筛选和排序。 Minimongo在客户端上速度非常快，通常你的数据少得多，所以不要担心性能。

在你的constructor中：

var allReviews = Reviews.find({});

改为使用：

var allReviews = Reviews.find(
  {
    class : (this.getReactively('selectedClass'))._id,
    visible : 1
  },
  {limit: 700}
);

另一个提示：javascript是关于 truthy 和 falsy 值的quite clever。

if (courseId != undefined && courseId != "" && visibility == 1)

可以简化为：

if (courseId && visibility)

假设您使用visibility == 1表示true而visibility == 0表示false

订阅包含先前订阅结果

1 个答案: