Null ng-false-value

null-false-value.js

;(function(){
'use strict'

// Sets falsy values as null on the model. This does not seem to be possible
// using ng-false-value, since it sets it as "null" (string) instead.
// usage <input type="checkbox" ng-model"model.attr" null-false-value />

angular.module('yourModule')

  .directive('nullFalseValue', function(_){
    return {
      require: 'ngModel',
      link: function(scope, el, attrs, ctrl){
        var ngModel = ctrl
        var parserSet

        function parser(inputVal){
          return inputVal || null
        }

        function setParser() {
          if (!parserSet) parserSet = ngModel.$parsers.push(parser)
        }

        // Angular 1.2 runs the input directive logic in a post-link function...
        // since ngModel requires the input directive, and we require ngModel, 
        // there is no way to run our $parser after the input directive $parser.
        // so the (gulp) hack is to insert it on the first change/focus event.
        el.one('focus', setParser)
        el.one('change', setParser)
      }
    }
  })
})()