Problem

You want to validate your form text fields. The validation should only apply when the user focused out of the input (so that a blank form won’t be all-red until user focuses each field).

Solution

Create a new component and define a focusOut hook, which will record that the field has been focused, and add a computed property named hasError, which will return validation result only if the field has been focused. The component expects to get the validation result as the valid property.

  1. App.ValidatedInputComponent = Ember.Component.extend({
  2.   beenFocused: false,
  3.   valid: null,
  4.   hasError: function() {
  5.     if (this.get('beenFocused')) {
  6.       return !this.get('valid');
  7.     }
  8.   }.property('valid', 'beenFocused'),
  9.   focusOut: function() {
  10.     this.set('beenFocused', true);
  11.   }
  12. });

And in the template of the component, put an {{input}} and wrap it into a div, which would have the class of has-error bound to hasError. 

  1. <script type="text/x-handlebars" data-template-name="components/validated-input">
  2.   <div {{bindAttr class="hasError :form-group"}}>
  3.     {{input type=type value=value size=size pattern=pattern name=name placeholder=placeholder disaled=disabled maxlength=maxlength tabindex=tabindex class=input-class}}
  4.   </div>
  5. </script>

The use like this:

  1. {{validated-input value=name valid=nameValid placeholder="Name" type="text" input-class="form-control"}}

Discussion

Essentially, what we need to achieve is to have a component which wraps the input field with a div that has the has-error class if the validation fails (after the field has been focused). The validation result is passed to the component through the valid property.

As there is no way to take existing Ember.TextField component and wrap it with a layout (because <input> is a self-closing element, so it has no content, and so there is nothing to wrap; and Ember can’t wrap the element itself this way), we are creating a new component, ValidatedInputComponent.

It renders a wrapped input field. The wrapper has the has-error class if hasError property of the component is true. It’s true only when the validation fails and the field has been focused at.

Example

JS Bin