javascript - angular checkbox does not bind to model -

in controller have member:

$scope.sameoptionsonreturn = true; 

and in view:

<input type="checkbox"        ng-model="sameoptionsonreturn"        ng-checked="sameoptionsonreturn"        ng-value="true"        ng-change="setreturnoptions" /> 

but input not bind checkbox; it's true. wrong?

note: removing ng-value="true" doesn't make difference.

since work in snippet below, have assume there's wrong elsewhere in code.

function supercontroller($scope) {  	$scope.sameoptionsonreturn = true;  }    angular.module('myapp', []);  angular      .module('myapp')      .controller('supercontroller', supercontroller)

<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.5.6/angular.min.js"></script>  <div ng-app="myapp">    <div ng-controller="supercontroller s">      <input type="checkbox"         ng-model="sameoptionsonreturn"         ng-checked="sameoptionsonreturn"         ng-value="true"         ng-change="setreturnoptions" />            {{sameoptionsonreturn}}    </div>  </div>