HAML如果定义了？评估Middleman数据文件中是否存在条目的语句

Question

我有Middleman data file data/testimonials.yaml：

tom:
  short: Tom short
  alt: Tom alt (this should be shown)
  name: Thomas

jeff:
  short: Jeff short
  alt: Jeff alt (this should be shown)
  name: Jeffrey

joel:
  short: Joel short (he doesn't have alt)
  name: Joel

它可以有默认＆＃34;短＆＃34;文字或替代文字。对于一些推荐，我想在某些页面上使用替代文本，同时使用＆＃34; short＆＃34;别人的文字。

在我的test.haml我试图编写HAML语句来检查是否存在替代文本。如果是，则应插入;如果不是，则应使用标准文本。

以下示例显示data.testimonials[person].alt正确引用数据中的信息，因为它可以手动插入。但是，当我在if defined?语句中使用相同的变量时，它永远不会返回true。

Not-working 'if' way, because 'if defined?' never evaluates to true:
- ['tom','jeff','joel'].each do |person|
    %blockquote
        - if defined? data.testimonials[person].alt
            = data.testimonials[person].alt
        - else
            = data.testimonials[person].short

Manual way (code above should return exactly this):
- ['tom','jeff'].each do |person|
    %blockquote
        = data.testimonials[person].alt

- ['joel'].each do |person|
    %blockquote
        = data.testimonials[person].short

结果如下：

我做错了什么？有没有办法使用检查数据是否存在的条件语句？

Answer 1

defined? does not really do what you want. You can just just leave it away, the if will just evaluate to false because the value will be nil for alt.

So just put

- ['tom','jeff','joel'].each do |person|
    %blockquote
        - if data.testimonials[person].alt
            = data.testimonials[person].alt
        - else
            = data.testimonials[person].short

Or you could actually write it much shorter:

- ['tom','jeff','joel'].each do |person|
    %blockquote
        = data.testimonials[person].alt || data.testimonials[person].short

I don't really know for sure, why defined? does not work, but generally you don't need the method to check for it, because undefined values will just give you a nil in middleman.