角：表單驗證和定製指令

Question

我有兩個輸入端和我需要驗證各字段具有下列限制：B值必須總是輕微比值一個否則顯示出錯誤消息。這是example。

我知道我需要創建一個指示，但我不知道，甚至如何下手。

HTML

<form name="exampleForm"> 
    <label>Value A</label> 
    <input type="number" name="valueA" data-ng-model="valueA" required="required"/> 
    <div ng-messages="exampleForm.valueA.$error"> 
     <div ng-message="required">This field is required</div> 
    </div> 
    <p> 
    <label>Value B</label> 
    <input type="number" name="valueB" data-ng-model="valueB" required="required"/> 
    <div ng-messages="exampleForm.valueB.$error"> 
     <div ng-message="required">This field is required</div> 
    </div> 
</form> 

Answer 1

<input type="number" name="valueB" data-ng-model="valueB" max="{{ valueA - 1 }}" required="required"/> 
    <div ng-messages="exampleForm.valueB.$error"> 
    <div ng-message="required">This field is required</div> 
    <div ng-message="max">This field is too large</div> 
    </div>