Angularjs -如何在表单验证中比较两个以上的输入值

<form name="myForm">
  <input type="password" name="password" ng-model="user.password" required>
  <input type="password" name="confirmPassword" ng-model="user.confirmPassword" required>
</form>

app.controller('myController', function($scope) {
  $scope.user = {};

  $scope.checkPasswords = function() {
    return $scope.user.password === $scope.user.confirmPassword;
  };
});

<form name="myForm">
  <input type="password" name="password" ng-model="user.password" required>
  <input type="password" name="confirmPassword" ng-model="user.confirmPassword" ng-pattern="checkPasswords()" required>
  <span ng-show="myForm.confirmPassword.$error.pattern">Passwords do not match.</span>
</form>