访问验证错误消息自定义指令

Question

<form-input label="Product Name" required name="name" model="ProdEdit.product.title"></form-input>

App.directive('formInput', function($timeout) {
    var template = '<div class="form-group">'+
    '<label for="{{id}}">{{label}}</label>'+
    '<input type="text" required name="{{name}}" class="form-control" ng-model="model" id="{{id}}" placeholder="Enter {{label}}">'+
    '<div ng-messages="myForm.name.$error" class="text-danger"></div>'+
'<span ng-message="required" >This is mandatory</span>'+
    '</div>';
    return {
      restrict: 'E',
      require: "^ngMessages",
      template: template,
      scope: {
        label: "@",
        model: "=",
        name: "@",
        required : "&"
      },
      replace: true
    };
  })

我创建了一个表单输入指令，如上所述。现在我想在span中显示错误消息。请帮助我。