javascript - 尝试获取平均评分时出现错误模板助手中出现异常 : TypeError: Cannot read property 'rating' of null

Question

我有两个菜谱和评论集合，用户可以评论一个菜谱，并可以从 1 到 5 对其进行评分，我试图获得菜谱的平均评分，但出现错误模板助手中出现异常:TypeError:无法读取属性“评级”为 null您能指导我犯了什么错误以及如何解决它吗？

collections.js

Recipes = new Mongo.Collection('recipes');
Reviews = new Mongo.Collection('reviews');

add_review.js

Template.add_review.events({
    'submit .add-review':function(event){
        var rating = event.target.rating.value;
        var review = event.target.review.value;
            Reviews.insert({
                rating:rating,
                review:review,
                recipeId:Router.current().data()._id
            });

        return false;
})

获得平均评分的 helper

Template.reviews.helpers({

    averageRating: function() {
        var reviews = Reviews.find({recipeId: Router.current().data()._id});
        var ratings = _.pluck(reviews, 'rating');
        var sum = ratings.reduce(function(pv, cv){return pv + cv;}, 0);
        var avg = sum / ratings.length;
        return Math.round(avg);
    }
})

Answer 1

find返回一个光标。为了使评论成为数组，您需要使用 fetch像这样:

var reviews = Reviews.find({recipeId: Router.current().data()._id}).fetch();

另请注意，您需要防止评级为空数组的情况。在这种情况下，您的平均值将返回Infinity。也许是这样的:

Template.reviews.helpers({
  averageRating: function() {
      var selector = {recipeId: Router.current().data()._id};
      var reviews = Reviews.find(selector).fetch();

      if (reviews.length === 0)
        return 0;

      var ratings = _.pluck(reviews, 'rating');
      var sum = ratings.reduce(function(pv, cv){return pv + cv;}, 0);
      var avg = sum / ratings.length;
      return Math.round(avg);
  }
});

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