[angularjs] Angularjs prevent form submission when input validation fails

I know it's late and was answered, but I'd like to share the neat stuff I made. I created an ng-validate directive that hooks the onsubmit of the form, then it issues prevent-default if the $eval is false:

app.directive('ngValidate', function() {
  return function(scope, element, attrs) {
    if (!element.is('form'))
        throw new Error("ng-validate must be set on a form elment!");

    element.bind("submit", function(event) {
        if (!scope.$eval(attrs.ngValidate, {'$event': event}))
            event.preventDefault();
        if (!scope.$$phase)
            scope.$digest();            
    });
  };
});

In your html:

<form name="offering" method="post" action="offer" ng-validate="<boolean expression">