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[英]Handlebars if statement condition show content based on membershipID
[英]Handlebars condition based on lookup
我有以下数据结构:
{
things: [
"desk",
"chair",
"pen",
"book",
"lamp"
],
owners: [
"Julia",
"Sandra",
"John",
"Paul"
]
}
工作原理:
此handleblars
模板:
{{#each things}}
<p>This {{this}} belongs to {{lookup ../owners @index}}</p>
{{/each}}
正确输出:
This desk belongs to Julia
This chair belongs to Sandra
This pen belongs to John
This book belongs to Paul
This lamp belongs to
什么不起作用:
现在,我想添加一个条件,因为最后一thing
可能没有owner
。 模板将如下所示:
{{#each things}}
{{#if lookup ../owners @index}}
<p>This {{this}} belongs to {{lookup ../owners @index}}</p>
{{else}}
<p>...But this {{this}} belongs to nobody</p>
{{/if}}
{{/each}}
输出:
This desk belongs to Julia
This chair belongs to Sandra
This pen belongs to John
This book belongs to Paul
...But this lamp belongs to nobody
不幸的是,此{{#if lookup ../owners @index}}
无效。
我的问题:是否可以使用内置的Handlebars帮助器来实现,还是必须编写自定义帮助器?
我认为如果更改数据结构会更好,例如:
[
{
thing: "desk",
owner: "Julia"
},
{
thing: "chair",
owner:"Sandra"
},
{
thing: "pen",
owner: "John"},
{
thing: "book",
owner: "Paul"},
{
thing: "lamp"
}
]
那么您的车把模板将看起来像
{{#each this}}
{{#if this.owner}}
<p>This {{this.thing}} belongs to {{ this.owner}}</p>
{{else}}
<p>...But this {{this.thing}} belongs to nobody</p>
{{/if}}
{{/each}}
这将输出(我在http://tryhandlebarsjs.com/上运行了它)
<p>This desk belongs to Julia</p>
<p>This chair belongs to Sandra</p>
<p>This pen belongs to John</p>
<p>This book belongs to Paul</p>
<p>...But this lamp belongs to nobody</p>
使用车把帮手对您来说看起来不错,但从长远来看,将逻辑从车把移到javascript 会更好。
我相信,如果您想将Handlebars lookup
与if
嵌套在一起,答案是“否”。
但在这里,如果你想省略最后的thing
(或n东西),它不具有owner
,您可以反向检查#each
像下面,
{{#each owners}}
<p>This {{lookup ../things @index}} belongs to {{this}}</p>
{{/each}}
哪个输出,
<p>This desk belongs to Julia</p>
<p>This chair belongs to Sandra</p>
<p>This pen belongs to John</p>
<p>This book belongs to Paul</p>
希望这可以帮助。
我通过编写自定义帮助程序isIndexExist
找到了另一种解决方案。
Handlebars.registerHelper("isIndexExist", function(array, value, options) {
return value < array.length ? options.fn(this) : options.inverse(this);
});
在模板中,您可以编写
{{#each things}}
{{#isIndexExist ../owners @index}}
<p>This {{this}} belongs to {{lookup ../owners @index}}</p>
{{else}}
<p>...But this {{this}} belongs to nobody</p>
{{/isIndexExist}}
{{/each}}
希望这可以帮助。
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