Class Helper

import Helper from '@ember/component/helper';

Ember Helpers are functions that can compute values, and are used in templates. For example, this code calls a helper named format-currency:

<div>{{format-currency cents currency="$"}}</div>

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:

{{show-money amount=(format-currency cents currency="$")}}

Helpers defined using a class must provide a compute function. For example:

import Helper from '@ember/component/helper';

export default 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.