Question

I would like to automatically highlight a Ember.TextField when the value in it is invalid.

I have something like this in my template right now that works but is ugly:

{{#if view.fieldInvalid}}
    {{view Ember.TextField valueBinding="view.fieldValue" classNames="span1p5 highlight"}}
{{else}}
    {{view Ember.TextField valueBinding="view.fieldValue" classnames="span1p5"}}
{{/if}}

Is there a way to do this in Ember.JS with a built-in view like Ember.TextField?

Answer 1

One way of doing this is adding a classname bindings with computed property

//First extend Ember.TextField in your view
validatingTextField = Ember.TextField.extend({
  //Now if isInvalid is true CSS class "highlight" is applied to text field
  /* other ways include 
     isValid::error-class error-class will be applied when isValid is false
     isValid:normal-class:error-class, normal-class is applied when isValid is true else error-class is applied
  */ 
  classNameBindings: ['isInvalid:highlight',':span1p5'],
  //If you have static classes you define them as :my-class-name
  isInvalid: function(){
    if(this.get('value').trim() === ""){
      return true;
    }else{
      return false;
    }
  }.property('value')
})

Now use the above defined in your handlebars

{{view view.validatingTextField valueBinding="view.fieldValue"}}

Important
The above code may satisfy your need but may slow down your application if there are many text-fields, as the computed property is executed for every single change in the value, it is better to have a save button action which on click may apply the CSS class to the textfield as follows

validatingTextField = Ember.TextField.extend({
  classNameBindings: ['isInvalid:highlight',':span1p5']
})

save: function(){
  //your code for save
  if(this.get('validatingTextField.value').trim()===""){
    this.get('validatingTextField').set('isInvalid', true);
  }
}