Custom form validation directive to compare two fields

Question

I\'m an angular newbie, and I\'m stumbling over something in how angular\'s form validation directives work.

I know that I can fairly easily add directives to in

Answer 1

Many ways to skin a cat.

PLUNKER

app.directive('lowerThan', [
  function() {

    var link = function($scope, $element, $attrs, ctrl) {

      var validate = function(viewValue) {
        var comparisonModel = $attrs.lowerThan;

        if(!viewValue || !comparisonModel){
          // It's valid because we have nothing to compare against
          ctrl.$setValidity('lowerThan', true);
        }

        // It's valid if model is lower than the model we're comparing against
        ctrl.$setValidity('lowerThan', parseInt(viewValue, 10) < parseInt(comparisonModel, 10) );
        return viewValue;
      };

      ctrl.$parsers.unshift(validate);
      ctrl.$formatters.push(validate);

      $attrs.$observe('lowerThan', function(comparisonModel){
        // Whenever the comparison model changes we'll re-validate
        return validate(ctrl.$viewValue);
      });

    };

    return {
      require: 'ngModel',
      link: link
    };

  }
]);

Usage:

  Min cannot exceed max.