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EmberJS 使用@each計(jì)算屬性和聚合數(shù)據(jù)
2018-01-03 14:54 更新
使用@each計(jì)算屬性和聚合數(shù)據(jù)
computed屬性訪(fǎng)問(wèn)數(shù)組中的所有項(xiàng)目以確定其值。它使得簡(jiǎn)單的添加項(xiàng)目和從數(shù)組中刪除項(xiàng)目。依賴(lài)鍵包含特殊鍵 @each ，不要使用嵌套形式的@each。這將更新當(dāng)前計(jì)算屬性的binding和observer。
App.TodosController = Ember.Controller.extend({
todos:[
Ember.Object.create({ isDone: true }),
Ember.Object.create({ isDone: false }),
Ember.Object.create({ isDone: true })
],
remaining: function() {
var todos = this.get('todos');
return todos.filterBy('isDone', false).get('length');
}.property('todos.@each.isDone')
});
在上面的代碼中， todos.@each.isDone 依賴(lài)項(xiàng)鍵包含一個(gè)特殊鍵@each。當(dāng)您從Todo中添加和刪除內(nèi)容時(shí)，此鍵激活觀(guān)察器。它將在剩余的計(jì)算屬性中更新。
例子
<!DOCTYPE html>
<html>
<head>
<title>Emberjs Computed Properties and Aggregate Data with @Each</title>
<!-- CDN's-->
<script src="/attachements/w3c/handlebars.min.js"></script>
<script src="/attachements/w3c/jquery-2.1.3.min.js"></script>
<script src="/attachements/w3c/ember.min.js"></script>
<script src="/attachements/w3c/ember-template-compiler.js"></script>
<script src="/attachements/w3c/ember.debug.js"></script>
<script src="/attachements/w3c/ember-data.js"></script>
</head>
<body>
<script type="text/javascript">
App = Ember.Application.create();
//Extending the Ember.Controller
App.TodosController = Ember.Controller.extend({
//todos is an array which holds the boolean values.
todos: [
Ember.Object.create({ isDone: true }),
Ember.Object.create({ isDone: false }),
Ember.Object.create({ isDone: true })
],
//dispaly the remainig values of todos
remaining: function() {
var todos = this.get('todos');
//returnt the todos array.
return todos.filterBy('isDone', false).get('length');
}.property('todos.@each.isDone')
});
var car_obj = App.TodosController.create();
document.write("The remaining number of cars in todo list: "+car_obj.get('remaining'));
</script>
</body>
</html>
輸出
讓我們執(zhí)行以下步驟，看看上面的代碼如何工作：
將上述代碼保存在 computed_prop_agg_each.html 文件中
在瀏覽器中打開(kāi)此HTML文件。
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