基于查找的把手条件 [英] Handlebars condition based on lookup

问题描述

我有以下数据结构：

  {
 things：[
desk， 
椅子，
笔，
书，
灯
]，
所有者：[
Julia ，
Sandra，
John，
Paul
] 
} 
  

$ b $ p 什么工作：

handleblars b
$ b pre $ {code} {{＃each things}}
< p>这{{this} }属于{{lookup ../owners @index}}< / p>
{{/ each}}

正确输出：

 这张桌子属于Julia 
这张椅子属于Sandra 
这支笔属于John 
这本书属于Paul 
此灯属于
  

什么不起作用：

现在，我想添加一个条件，因为最后一个事物可能没有 owner 。然后，模板将如下所示：

  {{＃each things}} 
 {{#if lookup .. / owners @index}} 
< p>此{{this}}属于{{lookup ../owners @index}}< / p> 
 {{else}} 
< p> ...但这{{this}}属于任何人< / p> 
 {{/ if}} 
 {{/ each}} 
  

输入：

 这张桌子属于Julia 
这把椅子属于Sandra 
这支笔属于John 
这本书属于保罗
 ......但是这个灯属于无人
  

不幸的是，这个 {{＃if lookup ../owners @index}} 这个东西不能用。

我的问题：是否有可能通过内置的Handlebars助手实现这一点，还是我必须编写一个自定义助手？

解决方案

我认为如果你想改变你的数据结构会更好，比如像这样：

 <$ c 
 $ b $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ 
所有者：Sandra
}，
 {
东西：笔，
所有者：John}， 
 {
 thing：book，
 owner：Paul}，
 {
 thing：lamp
} 
] 
  

那么你的车把模板看起来就像

 {{＃this this}} 
 {{#if this.owner}} 
< p>这{{this.thing}}属于{ this.owner}}< / p为H. 
 {{else}} 
< p> ...但这{{this.thing}}属于任何人< / p> 
 {{/ if}} 
 {{/ each}} 
  

this会输出（我在 http://tryhandlebarsjs.com/ 上运行它）

 < p>这张桌子属于Julia< / p> 
< p>这张椅子属于Sandra< / p> 
< p>这支笔属于John< / p> 
< p>本书属于Paul< / p> 
< p> ...但此灯属于任何人< / p> 
  

使用手柄助手可能看起来不错，但是将逻辑从手柄移动到javascript / strong>长远来说会更好。

I have the following data structure:

{
    things: [
        "desk",
        "chair",
        "pen",
        "book",
        "lamp"
    ],
    owners: [
        "Julia",
        "Sandra",
        "John",
        "Paul"
    ]
}

What's working:

This handleblars template:

{{#each things}}
    <p>This {{this}} belongs to {{lookup ../owners @index}}</p>
{{/each}}

Correctly outputs:

This desk belongs to Julia
This chair belongs to Sandra
This pen belongs to John
This book belongs to Paul
This lamp belongs to

What's not working:

Now, I'd like to add a condition because the last thing might not have an owner. The template would then look something like:

{{#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}}

And the ouput:

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

Unfortunately, this {{#if lookup ../owners @index}} thing doesn't work.

My question: is it possible to achieve this with built-in Handlebars helpers, or do I have to write a custom helper?

解决方案

I think it will be better if you were to change your data structure, for instance like this:

[
        {   
            thing:    "desk",
            owner: "Julia"
        },
        {   
            thing: "chair",
            owner:"Sandra"
        },
        {   
            thing:  "pen",
            owner:  "John"},
        {   
            thing:  "book",
            owner:  "Paul"},
        { 
            thing:  "lamp"
        }
]    

then your handlebar template will look like

{{#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}}

this will output (I ran it on http://tryhandlebarsjs.com/)

<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>

Using handlebars helpers may look good to you, but moving logic from handlebars to javascript will be better in long run.

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