Ng-model does not update controller value

"If you use ng-model, you have to have a dot in there."
Make your model point to an object.property and you'll be good to go.

Controller

$scope.formData = {};
$scope.check = function () {
  console.log($scope.formData.searchText.$modelValue); //works
}

Template

<input ng-model="formData.searchText"/>
<button ng-click="check()">Check!</button>

This happens when child scopes are in play - like child routes or ng-repeats. The child-scope creates it's own value and a name conflict is born as illustrated here:

See this video clip for more: https://www.youtube.com/watch?v=SBwoFkRjZvE&t=3m15s

Controller as version (recommended)

Here the template

<div ng-app="example" ng-controller="myController as $ctrl">
    <input type="text" ng-model="$ctrl.searchText" />
    <button ng-click="$ctrl.check()">Check!</button>
    {{ $ctrl.searchText }}
</div>

The JS

angular.module('example', [])
  .controller('myController', function() {
    var vm = this;
    vm.check = function () {
      console.log(vm.searchText);
    };
  });

An example: http://codepen.io/Damax/pen/rjawoO

The best will be to use component with Angular 2.x or Angular 1.5 or upper

########

Old way (NOT recommended)

This is NOT recommended because a string is a primitive, highly recommended to use an object instead

Try this in your markup

<input type="text" ng-model="searchText" />
<button ng-click="check(searchText)">Check!</button>
{{ searchText }}

and this in your controller

$scope.check = function (searchText) {
    console.log(searchText);
}