AngularJS – Directive 介紹篇
接續前面提到的關於產品展示頁面的製作，我們在HTML文件上面加入一個Add to Cart的按鈕，但是希望這個按鈕可以有條件性的顯示或隱藏，我們可以在該按鈕的HTML標籤中加入ng-show=”store.product.canPurchase”的屬性，這個屬性會去判斷在gem數列中canPurchase中的值是否為true，若不是則該按鈕不顯示於畫面上，反之則會顯示加入購物車（Add to Cart）的按鈕。
在這個案例中canPurchase就算是在數列中的顯示參數，其實這個參數並不是一定要叫canPurchase這個名稱，可以自行決定名稱，例如在馬老師製作的案例中，我就是利用buttonShow這樣的參數名稱，大家也可以在JS Bin上面看看這個案例的程式碼。
<!DOCTYPE html>
<html ng-app="store">
<head>
<meta name="description" content="AngularJS directivesExample 1">
<script src="//ajax.googleapis.com/ajax/libs/angularjs/1.3.2/angular.min.js"></script>
<meta charset="utf-8">
<title>AngularJS directivesExample 1</title>
</head>
<body>
<div ng-controller="StoreController as store">
<h1>{{ store.product.name }}</h1>
<h2>NT${{ store.product.price }}</h2>
<p>{{ store.product.description }}</p>
<button ng-show="store.product.buttonShow">加入購物車</button>
</div>
</body>
</html>
(function(){
var app = angular.module('store',[]);
app.controller('StoreController',function(){
this.product = item;
});
var item = {
name:"馬老師雲端研究室 滑鼠墊",
price:"350",
description:"有些人認為滑鼠墊就只是種簡單的產品。無非是將滑鼠放於上方並將之滑來拖去。 “表面”上來說確實如此（一語雙關）。但實際上，製造能帶來卓越遊戲體驗的滑鼠墊卻需要結合眾多科學、技術和工藝。身為遊戲滑鼠技術的世界領先者，對如何使滑鼠感測器高效運作我們獨樹一幟。運用專門知識來製造適合的滑鼠墊表面，讓滑鼠感測器得以作出高效而精確的反應。",
buttonShow: false
};
})();
另外還有一種資料顯示的手法，我們可以在gem數列中另外加入soldOut這個參數，而在div的HTML標籤中加入ng-show=”!store.product.soldOut”這樣的屬性，其中驚嘆號指的是不等於，所以這個屬性的意思即是當soldOut參數不等於true的時候要隱藏該div，也就是會隱藏所有的商品資訊。
不過這樣的表達方式並不是很直接，必須要做邏輯上的轉換，因為條件式是soldOut不等於true就顯示該商品，不是很容易搞懂，所以同樣的案例我們可以把HTML中的標籤的屬性改成ng-hide=”store.product.soldOut”，這樣一來我們只需要去看soldOut參數中的值是true或是false，如果賣完就不顯示；沒賣完就顯示，這是一個比較直覺的方法，透過JS Bin觀賞本案例的原始碼。
接下來看多項商品的製作方式，首先必須了解如何在Javascript的數列中加入多項商品的資料。
輸入了以上數列的資料後，在HTML的頁面上可以依下圖的方式呈現出多重商品的資訊，不過從以下的呈現方式可以看的出來，如果商品數量不僅僅是只有兩項，那頁面上面的HTML標籤就會過於複雜，所以下面的方法僅僅是讓大家了解邏輯的部分。
實際上呈現的方式可以參考下圖，是不是簡單多了，在JS Bin上面觀看。
接下來幫大家整理目前講解到的一些AngularJS的專有名稱說明：
- Directives（指示） – 在HTML中觸發Javascript行為的參數。
- Modules（模組） – 定義我們的應用程式。
- Controllers（控制器） – 定義我們應用程式該如運作。
- Expressions（表達式） – 我們的資料該如何的顯示在頁面上。
※以上截圖部分為AngularJS官方教學視訊，另有directive指令介紹的專頁。
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