How to create ember handlebar helper?

Question

Hy to all

I try to create helper

Handlebars.registerHelper('testCan', function(permissionName, options){
  var permission = Ember.Object.extend({
    testCan: function(){
      debugger;
      return true;
    }.property()
  }).create();

  // wipe out contexts so boundIf uses `this` (the permission) as the context
  options.contexts = null;

  Ember.Handlebars.helpers.boundIf.call(permission, "testCan", options)
});

And use it as

{{#testCan read controller=controller}}
    <h1>It's works</h1>
{{/testCan}}

I do this to test pattern from here http://livsey.org/blog/2012/10/16/writing-a-helper-to-check-permissions-in-ember-dot-js/

But it doesn't work ((

What's wrong? Ember version - 1.9.1

P.P.S originally i work with existing code ( see here Ember.handlebars boundIf didn't call calculated property ) But this example i've got on trying reproduce / resolve that problem

Yep. Trouble in next - i create symple helper in ember ember-cli project. But when i copy it into working project - it doesn't work (( — Vasiliy vvscode Vanchuk, Mar 21 '15 at 18:10

Samsinite · Accepted Answer · 2015-03-21T20:03:12.083

It might be simplest to use an existing add-on if you are trying to check for permissions/authorization. I suggest ember-can or ember-sanctify (I believe sanctify only supports 1.10 and later).

What you are trying to do though might be easier to reason about inside of a component. In practice the only reasons I suggest for creating helpers is to either do simple conversions or to be able to pass an arbitrary number of args. One of the things Ember could improve on, is helping users understand how do more complex stuff inside of a helper.

Example Component:

app/templates/components/test-can.hbs:

{{#boundIf hasPermission}}
  {{yield}}
{{/boundIf

app/components/test-can.js:

import Ember from 'ember';

export default Ember.Component.extend({
  permission: null,
  controller: null,

  hasPermission: function() {
    //implement logic here
  }.property('permission', 'controller')
});

Example use:

{{#test-can permission=read controller=controller}}
  Your Content Here
{{/test-can}}

Not sure what read and controller are in your example, so if those variables are pointing to nothing, this wouldn't do much. Hope this helps.

Update:

So creating a file at app/helpers/test-can.js that looks like the following

export default function(permissionName, options){
  var permission = Ember.Object.extend({
    testCan: function(){
      return true;
    }.property()
  }).create();

  // wipe out contexts so boundIf uses `this` (the permission) as the context
  options.contexts = null;

  return Ember.Handlebars.helpers.boundIf.call(permission, "testCan", options);
}

Doesn't work when testing? The example above of course will always return true thus always yielding the block. 1.9.1 still basically uses the same code for the if helper.

Some times i should pass parametrs into helper - so i create custom helper instead of creating helper property into all models — Vasiliy vvscode Vanchuk, Mar 21 '15 at 19:05
Sorry, forgot the yield section in the example above. Is there a reason that one of the ember addons does not work for you? — Samsinite, Mar 21 '15 at 19:35
I have code, that work fine on current version of ember ( 1.7.0 ) Now i want to migrate onto newest version - so i takl about existing code ( original problem is here http://stackoverflow.com/questions/29182806/ember-handlebars-boundif-didnt-call-calculated-property - described case i fond on trying resolve it ) — Vasiliy vvscode Vanchuk, Mar 21 '15 at 19:43
I've got Handlebars error: Could not find property 'testCan' on object (generated application controller). — Vasiliy vvscode Vanchuk, Mar 21 '15 at 20:25

score 0 · Answer 2 · answered Mar 23 '15 at 08:15

Related issue https://github.com/emberjs/ember.js/issues/10692

The this context inside of helpers has changed in various versions:

this was the controller in 1.0.0 through 1.8.0 this was the view in 1.9.0 and 1.10.0 this is undefined in 1.11+ My guess is that the context change in 1.9 is causing this error, updating your helper to add the unknownProperty to the controller will fix the issue.

How to create ember handlebar helper?

2 Answers2

Update: