Change dynamically class in ionic with angular-formly

i have the next code, i want change the class when the value is equal to "abc" but i can't add some class : 

  $scope.formFields = [
    {
      key: 'email',
      type: 'input',
      templateOptions: {
        type:'email',
        placeholder: 'Correo',
        required:true,
        class: 'some-clase'
      }
    }]

now, I know well then the change is done but I can not even add a simple class :

  expressionProperties: {
        'templateOptions.class': '"glyphicon form-control-feedback glyphicon-"'
        }

help me please , if they can add an example in jsbin, codepen... thanks

Your expressionProperties property is a formly expression and can therefore be a function. It should probably be something more like this:

'templateOptions.class': function($viewValue, $modelValue, scope) {
  if ($viewValue === 'abc') {
    return 'some-class';
  } else {
    return 'some-other-class';
  }
}