Meteor.js：如何从事件中调用helper方法？

Question

I suspect I'm not doing this the Meteor way. I'm making a shared, interactive calendar.

I have a calendar template:

<template name="calendar">
<h2>Calendar</h2>
<div class="calendar">{{#each days}}
    {{> day}}
    {{/each}}
</div>
</template>

With a helper that returns a day object:

     {
        date: thisDate.getDate(),
        dateString: dateString,
        done: done,
        today: isToday
      }

I have a day template:

<template name="day">
  <div class="day {{stateString}}">{{date}}</div>
</template>

With some helpers ( meetingID is hardcoded for now for development):

  Template.day.helpers({
    state: function(){
      // retreive from DB
      var s = Meetings.findOne({"_id":meetingID}).dates[this.dateString];
      return s;
    }
    stateString: function(){
      var stateString;

      switch(this.state){
        case -1: stateString = "unknown"; break;
        case 0: stateString = "unavailable"; break;
        case 1: stateString = "available"; break;
      }
      if(this.done) stateString = "done";

      return stateString;
    }
  });

state() gets the state from the db and stateString() picks the right class name for that state.

When you click on it, you cycle through states (1: available, 0: not available, -1: unknown):

  Template.day.events({
    "click": function(){
      if(this.done) return false;   // no state changes for past days!
      console.log(e);
      var newState = this.state + 1;
      if(newState > 1) newState = -1;

      var q = "dates."+this.dateString+"."+Meteor.userId()+".state";
      console.log(q+ " / "+this.state+" / "+newState);
      Meetings.update(meetingID, {$set:{q:newState}});

      return false;
    }
  })

I'm having at least two specific problems:

1) How do I call the state() helper from the click event? 2) My db update doesn't seem to work—it's creating a 'q' document instead of using the string stored in q.

I'm sure this is missing some fundamental understanding of the right way to do this—please help!

Answer 1

Just expanding on the answer by @mark. You probably want to store state as a reactive variable so that your stateString helper will update when the state changes. If I understand correctly, you are not actually trying to use the state helper in your template - it is just needed for the string helper and the event. First add the reactive-var package:

meteor add reactive-var

I would recommend doing something like this for your template:

Template.day.created = function() {
  this.state = new ReactiveVar();
  this.autorun(_.bind(function() {
    var meetingDates = Meetings.findOne(meetingID).dates[this.data.dateString];
    var currentState = meetingDates[Meteor.userId()].state;
    this.state.set(currentState);
  }, this);
};

Template.day.helpers({
  stateString: function() {
    if (this.done) {
      return 'done';
    }
    switch(Template.instance().state.get()) {
      case -1: return 'unknown';
      case 0: return 'unavailable';
      case 1: return 'available';
    }
  }
});

Template.day.events({
  'click': function(event, template) {
    if (this.done) {
      return;
    }

    var newState = template.state.get() + 1;
    if (newState > 1) {
      newState = -1;
    }

    var modifier = {$set: {}}
    modifier.$set['dates.'+this.dateString+'.'+Meteor.userId()+'.state'] = newState;

    Meetings.update(meetingID, modifier);
  }
});

Answer 2

从任何地方访问模板助手：

Template.<name>.__helpers.get('<helper>').call()

Answer 3

Off the top of my head, one way to persist data between helpers and events in the same template is to store it as a property inside the template instance. So for example, you might have something that looks like this:

Template.day.created = function () {
  // here `this` refers to template instance
  this.state = -1;
};

Template.day.helpers({
  state: function () {
    var s = Meetings.findOne({"_id":meetingID}).dates[this.dateString];
    Template.instance().state = s;
    return s;
  },
  ...
});

Template.day.events({
  'click': function () {
    ...
    var state = Template.instance().state;
    ...
  }
});

As for the issue with q , you have to construct the object prior, otherwise q will be interpreted as the actual field name rather than a variable (notice how there's no distinction between "q" and q inside the query).

var query = {};
query[q] = newState;
Meetings.update(meetingID, { $set: query });

Hope this helps!