Class Ember.Helper
publicEmber Helpers are functions that can compute values, and are used in templates.
For example, this code calls a helper named format-currency
:
Additionally a helper can be called as a nested helper (sometimes called a
subexpression). In this example, the computed value of a helper is passed
to a component named show-money
:
Helpers defined using a class must provide a compute
function. For example:
1 2 3 4 5 6 7 |
export default Ember.Helper.extend({ compute(params, hash) { let cents = params[0]; let currency = hash.currency; return `${currency}${cents * 0.01}`; } }); |
Each time the input to a helper changes, the compute
function will be
called again.
As instances, these helpers also have access to the container an will accept injected dependencies.
Additionally, class helpers can call recompute
to force a new computation.
compute (params, hash) public
Defined in packages/ember-glimmer/lib/helper.js:88
Available since v1.13.0
- params
- Array
- The positional arguments to the helper
- hash
- Object
- The named arguments to the helper
Override this function when writing a class-based helper.
helper (helper) public
Defined in packages/ember-glimmer/lib/helper.js:103
Available since v1.13.0
- helper
- Function
- The helper function
In many cases, the ceremony of a full Ember.Helper
class is not required.
The helper
method create pure-function helpers without instances. For
example:
1 2 3 4 5 6 |
// app/helpers/format-currency.js export default Ember.Helper.helper(function(params, hash) { let cents = params[0]; let currency = hash.currency; return `${currency}${cents * 0.01}`; }); |
recompute public
Defined in packages/ember-glimmer/lib/helper.js:60
Available since v1.13.0
On a class-based helper, it may be useful to force a recomputation of that
helpers value. This is akin to rerender
on a component.
For example, this component will rerender when the currentUser
on a
session service changes:
1 2 3 4 5 6 7 8 9 10 |
// app/helpers/current-user-email.js export default Ember.Helper.extend({ session: Ember.inject.service(), onNewUser: Ember.observer('session.currentUser', function() { this.recompute(); }), compute() { return this.get('session.currentUser.email'); } }); |