模板助手被多次调用

Question

My intention is to retrieve one random entry from a collection and display it on the website - if all sentences are through (read: the user has "seen" them), display something else (therefore a dummy sentence gets returned). But, on server start and on button-click events, this helper gets fired at least twice. Here is some code:

In client.js:

Template.registerHelper('random_sentence', function() {
  fetched = _.shuffle(Sentences.find({
    users: {
      $nin: [this.userId]
    }
  }).fetch())[0];
  if (fetched === undefined) {
    return {
      sentence: "done",
      _id: 0,
      done: true
    };
  }
  Session.set('question', fetched._id);
  console.log(fetched);
  return fetched;
  });

The helper function for the template:

sent: function(){
  sent = Session.get('question');
  return Sentences.findOne(sent);
}

in main template:

{{#with random_sentence}}
  {{#if done}}
    <!-- Display something else -->
  {{else}}
    <div class="container">
      {{> question}}
    </div>
  {{/if}}
{{/with}}

the "question" template:

<div class="well">
  <div class="panel-body text-center">
    <h3>{{sent.sentence}}</h3>
  </div>
</div>

If I don't return anything in the "random_sentences"-function,nothing get's displayed.

I don't know where my "logic failure" is situated? I'm new to meteor - so I might overlook something obvious.

Thanks in advance :-)

UPDATE: This is how I intended to get the new sentence and display it:

Template.answer.events({
  'click': function(event) {
    var text = event.target.getAttribute('id');
    if (text !== null) {
      var question = Session.get('question');
      var setModifier = {
        $inc: {}
      };
    setModifier.$inc[text] = 1;
    Sentences.update(question, setModifier);
    Meteor.call('update_user', question);
    Notifications.success('Danke!', 'Deine Beurteilung wurde gespeichert.');
    Blaze.render(Template.question, document.head);
    }
  }
});

In server.js (updating the question and a counter on the user):

Meteor.methods({
  update_user: function(question) {
    Sentences.update(question, {
      $push: {
        "users": this.userId
      }
    });
    Meteor.users.update({
      _id: this.userId
    }, {
      $inc: {
        "profile.counter": 1
      }
    });
  },
});

I found the Blaze.render function somewhere on the web. the "document.head" part is simply because this function needs a DOM Element to render to, and since document.body just "multiplies" the body, I ust moved it to the head. (DOM logic isn't my strong part).

An Idea I had: would it make the whole idea simpler to implement with iron-router? atm. I wanted to create a "one-page app" - I therefore thought that I don't need a router there.

Another problem: Getting this logic to work (User gets one random sentence, which he has not seen) and publishing small sets of the collection (so the Client don't have to download 5 MB of data before using).

Answer 1

Template helpers can be called multiple times so it's good to avoid making them stateful. You're better off selecting the random entry in an onCreated or onRendered template handler. There you can do your random select, update the state, and put your choice in a Session variable to be retrieved by the helper.