情态动词

以下是一种纯粹的 Blaze 方法，用于将 UI 元素切换为存在和不存在。可以将其视为模态对话框的替代品。事实上，有很多方法可以使用这种方法实现模态对话框（只需添加背景蒙版和动画）。

文档对象模型

<template name="topicsPage">
  <div id="topicsPage" class="container">
    <div class="panel">
      <div class="panel-heading">
        Nifty Panel
      </div>
      <!-- .... -->
      <div class="panel-footer">
        <!-- step 1.  we click on the button object -->
        <div id="createTopicButton" class="btn {{ getPreferredButtonTheme }}">Create Topic</div>
      </div>
    </div>

    <!-- step 5 - the handlebars gets activated by the javascript controller -->
    <!-- and toggle the creation of new objects in our model -->
    {{#if creatingNewTopic }}
    <div>
      <label for="topicTextInput"></label>
      <input id="topicTextInput" value="enter some text..."></input>
      <button class="btn btn-warning">Cancel</button>
      <button class="btn btn-success">OK</button>
    </div>
    {{/if}}
  </div>
</template>

使用 Javascript

// step 2 - the button object triggers an event in the controller
// which toggles our reactive session variable
Template.topicsPage.events({
  'click #createTopicButton':function(){
    if(Session.get('is_creating_new topic'){
      Session.set('is_creating_new_topic', false);
    }else{
      Session.set('is_creating_new_topic', true);
    }
  }
});

// step 0 - the reactive session variable is set false
Session.setDefault('is_creating_new_topic', false);

// step 4 - the reactive session variable invalidates
// causing the creatNewTopic function to be rerun
Template.topicsPage.creatingNewTopic = function(){
  if(Session.get('is_creating_new_topic')){
    return true;
  }else{
    return false;
  }
}