如何在Handlebars的#each循环内访问外部user变量？

在Handlebars模板的{{#each}}循环中，由于this指向当前数组元素，无法直接访问外部传入的user变量，导致{{#if user.loggedIn}}判断始终返回假值，如何在循环内正确访问外部的user变量？

模板代码（appointment.hbs） #

{{#each this.classes}}
    <div class="divrow">
        <div class="container">
            <div id="imgdiv">
                <img class= "img-result" src="/images/{{this.photo}}" alt="Image1">  
            </div>    
            <div id="content-div">
                <h3>{{this.name}} and <em>{{this.email}}</em></h3>
                <p> {{this.age}} mins</p>

                {{#if user.loggedIn}}
                    <form action="/appointment/book" method="post">
                        <button type="submit" name="bookedClsId" value={{this._id}}>
                            Book Appointment
                        </button>
                    </form>
                {{else}}
                    <form action="/login" method="get">
                        <button type="submit" name="bookedClsId" value={{this._id}}>
                            Book Appointment
                        </button>
                    </form>
                {{/if}}
            </div>
        </div>
    </div>
{{/each}}

后端渲染代码（server.js） #

return res.render("classes", {layout: "layout",details: detailsFound , user: req.session.user});

Handlebars提供了@root特殊变量，用于访问模板的根级上下文（即通过res.render传入的最外层数据对象）。只需将循环内的user.loggedIn改为@root.user.loggedIn即可：

修改后的模板代码 #

{{#each this.classes}}
    <div class="divrow">
        <div class="container">
            <div id="imgdiv">
                <img class= "img-result" src="/images/{{this.photo}}" alt="Image1">  
            </div>    
            <div id="content-div">
                <h3>{{this.name}} and <em>{{this.email}}</em></h3>
                <p> {{this.age}} mins</p>

                {{#if @root.user.loggedIn}}
                    <form action="/appointment/book" method="post">
                        <button type="submit" name="bookedClsId" value={{this._id}}>
                            Book Appointment
                        </button>
                    </form>
                {{else}}
                    <form action="/login" method="get">
                        <button type="submit" name="bookedClsId" value={{this._id}}>
                            Book Appointment
                        </button>
                    </form>
                {{/if}}
            </div>
        </div>
    </div>
{{/each}}

后端的res.render代码无需修改，保持原样即可。

内容的提问来源于stack exchange，提问作者Amey079