ngMessages is a directive that is designed to show and hide messages based on the state
of a key/value object that it listens on. The directive itself compliments error message
reporting with the ngModel $error object (which stores a key/value state of validation errors).
ngMessages manages the state of internal messages within its container element. The internal
messages use the ngMessage directive and will be inserted/removed from the page depending
on if they're present within the key/value object. By default, only one message will be displayed
at a time and this depends on the prioritization of the messages within the template. (This can
be changed by using the ng-messages-multiple on the directive container.)
A remote template can also be used to promote message reuseability and messages can also be overridden.
Click here to learn more about ngMessages and ngMessage.
<!-- using attribute directives -->
<ANY ng-messages="expression">
  <ANY ng-message="keyValue1">...</ANY>
  <ANY ng-message="keyValue2">...</ANY>
  <ANY ng-message="keyValue3">...</ANY>
</ANY>
<!-- or by using element directives -->
<ng-messages for="expression">
  <ng-message when="keyValue1">...</ng-message>
  <ng-message when="keyValue2">...</ng-message>
  <ng-message when="keyValue3">...</ng-message>
</ng-messages>
| Param | Type | Details | 
|---|---|---|
| ngMessages | string | an angular expression evaluating to a key/value object (this is typically the $error object on an ngModel instance). | 
| ngMessagesMultiple
        | multiple (optional) | string | when set, all messages will be displayed with true | 
| ngMessagesInclude
        | include (optional) | string | when set, the specified template will be included into the ng-messages container | 
<form name="myForm">
  <label>Enter your name:</label>
  <input type="text"
         name="myName"
         ng-model="name"
         ng-minlength="5"
         ng-maxlength="20"
         required />
  <pre>myForm.myName.$error = {{ myForm.myName.$error | json }}</pre>
  <div ng-messages="myForm.myName.$error" style="color:maroon">
    <div ng-message="required">You did not enter a field</div>
    <div ng-message="minlength">Your field is too short</div>
    <div ng-message="maxlength">Your field is too long</div>
  </div>
</form>angular.module('ngMessagesExample', ['ngMessages']);