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Built-in Helpers

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In the last section you learned how to write a helper. A helper is usually a simple function that can be used in any template. Ember comes with a few helpers that can make developing your templates a bit easier. These helpers can allow you to be more dynamic in passing data to another helper or component. For a full list of built-in Helpers, see the Ember.Templates.helpers API documentation.

Using a helper to get a property dynamically

The {{get}} helper makes it easy to dynamically send the value of a variable to another helper or component. This can be useful if you want to output one of several values based on the result of a computed property.

{{get this.address this.part}}

if the part computed property returns "zip", this will display the result of this.address.zip. If it returns "city", you get this.address.city.

Nesting built-in helpers

In the last section it was discussed that helpers can be nested. This can be combined with these sorts of dynamic helpers. For example, the {{concat}} helper makes it easy to dynamically send a number of parameters to a component or helper as a single parameter in the format of a concatenated string.

{{get "foo" (concat "item" this.index)}}

This will display the result of this.foo.item1 when index is 1, and this.foo.item2 when index is 2, etc.

Built-in block helpers

Now let's say your template is starting to get a bit cluttered and you now want to clean up the logic in your templates. This can be achieved with the let block helper. The {{let}} helper lets you create new bindings in your template.

Say your template now looks like this:

Welcome back {{concat this.person.firstName ' ' this.person.lastName}}

Account Details:
First Name: {{this.person.firstName}}
Last Name: {{this.person.lastName}}

As mentioned in the previous section we use the concat helper to render both person.firstName and person.lastName in one go. We can use let to make a fullName variable in the template with the result of the concat:

{{#let (concat this.person.firstName this.person.lastName)
  as |fullName|
}}
  Welcome back {{fullName}}

  Account Details:
  First Name: {{this.person.firstName}}
  Last Name: {{this.person.lastName}}
{{/let}}

Now, as long as your template is wrapped in the let helper you can access the full name as fullName.

Array helper

Using the {{array}} helper, you can pass arrays directly from the template as an argument to your components.

<MyComponent @people={{array
    'Tom Dade'
    'Yehuda Katz'
    this.myOtherPerson}}
 />

In the component's template, you can then use the people argument as an array:

app/templates/components/my-component.hbs
<ul>
  {{#each this.people as |person|}}
    <li>{{person}}</li>
  {{/each}}
</ul>
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