Handlebar helper inside {{#each}}

Question

I try to call a registered handlebar helper inside a {{#each}} loop. Unfortunately Ember.js complains because it tries to resolve the helper as a property of the controller rather than a helper.

Handlebars.registerHelper('testHelper', function(name) {
    return 'foo: ' + name
});

(names and content are just dummy values to show the example)

{{#each entry in App.testController}}
   <div>{{{testHelper entry.name}}}</div>
{{/each}}

The error that the Ember.js prints is:

Uncaught Error:  Handlebars error: Could not find property 'testHelper' on object <App.testController:ember254>.

How do I need to call the registered helper so that it gets recognized?

Answer 1

Got it running, either with this solution,

Javascript

Handlebars.registerHelper('testHelper', function(property, options) {
  return 'foo: ' + Ember.get(options.data.view.content, property);
});

Handlebars template

<script type="text/x-handlebars" data-template-name='app-view'>
  <ul>
  {{#each entry in content}}
    <li>{{testHelper name}}</li>
  {{/each}}
  </ul>
</script>​

Or even better, with this one:

Javascript

Handlebars.registerHelper('testHelper', function(property) {
  return 'foo: ' + Ember.get(this, property);
});

Handlebars template

<script type="text/x-handlebars" data-template-name='app-view'>
  <ul>
  {{#each entry in content}}
    {{#with entry}}
      <li>{{testHelper name}}</li>
    {{/with}}
  {{/each}}
  </ul>
</script>​

Answer 2

My helpers are written in individual files, so I modified @MikeAski's answer to be the following.

In helpers/my-helper.js:

var MyHelper = function(value) {
    return moment(value).format("MMMM Do, YYYY");
};

export
default MyHelper;

At the top of app.js:

// import modules
import myHelper from 'appkit/helpers/my-helper';

// register custom helpers
Ember.Handlebars.registerBoundHelper('myHelper', myHelper);

Then you don't even need the {{#with}} in handlebars, just use as a normal helper.

{{#each thing}}
    {{myHelper thing.foo}}
{{/each}}

Answer 3

If you don't want to use a global helper then you could use a "pathed query":

{{#each entry in App.testController}}  
   <div>{{{../testHelper entry.name}}}</div>  
{{/each}}  

../ is the syntax for a pathed query. It causes you to traverse up the scope tree 1 level, and access private data from a parent scope. To traverse 2 levels upwards you could do the following ../../. This is useful if you have nested for-loops.