流星中的辅助功能是否具有反应性？

Question

Suppose I have the following code in my HTML file:

{{#if someVar}}
    {{>someTemplate}}
{{/if}}

Now, if initially someVar returns false then the someTemplate Template is not created. Now, due to some event, the value returned by someVar is true will the template be rendered or not? Do I need to make someVar a ReactiveVar for this to work? Or should I use autorun ? Which is the best and easiest method to do this? This can be achieved quite easily with 2-way binding in Angular.

Answer 1

Considering the given template above:

{{#if someVar}}
    {{>someTemplate}}
{{/if}}

Non-Reactive Example

var someNumber = 42; // changing this will not cause a new run

Template.theTemplate.helpers({
  someVar() {
    return someNumber;
  }
});

Reactive Example 1

var someNumber = new ReactiveVar(42); // changing this will cause a new run

Template.theTemplate.helpers({
  someVar() {
    return someNumber.get();
  }
});

Reactive Example 2

Template.theTemplate.onCreated(function onCreated() {
  this.someNumber = new ReactiveVar(42); // changing this will cause a new run
});

Template.theTemplate.helpers({
  someVar() {
    return Template.instance().someNumber.get();
  }
});

The forementioned 2-way binding is achieved automatically using ReactiveVar oder ReactiveDict.