如何更新Ember模板中的辅助体内的变量

Question

Imagine a property myNumber in a controller that has a different random number every second. With this template you will see this change every second:

<h4>Random number</h4>
<p>{{myNumber}}</p>

However, when the number is only referenced inside a helper (eg #if or #each ), the number is not updated anymore. This will only show the initial value:

<h4>Random number</h4>
{{#if model}}
    <p>{{myNumber}}</p>
{{/if}}

(Note that myNumber has no relation to model . Just using some random truthy property.)

Interestingly, when you add the reference to the property back to the root of the document, the previously static numbers will now also update:

<h4>Random number</h4>
{{myNumber}} -- Without this reference, references below won't update.
{{#if model}}
    <p>{{myNumber}}</p>
{{/if}}

How can I have myNumber inside the helpers update, without showing the number in the root of my template?

I've tried adding the reference in html comments, but that doesn't work. I assume Ember doesn't draw elements that are not in the DOM:

<h4>Random number</h4>
<!-- {{myNumber}} -->
{{#if model}}
    <p>{{myNumber}}</p>
{{/if}}

What does work is adding the value to the DOM, but hiding it. However, this is an ugly solution:

<h4>Random number</h4>
<span style="display:none">
    {{myNumber}}
</span>
{{#if model}}
    <p>{{myNumber}}</p>
{{/if}}

Answer 1

Using an arrow function will solve your problem.