How to get first item of Yaml list

support
1

I have the following .md file:

limits_section:
  title: Foo bar
  tabs:
    - title: Foo bar
      foo: bar
    - title Bar foo
      foo: bar

I can successfully iterate through it with {{ range .Params.limits_section.tabs }}

However, I am facing difficulties fetching the first element of the list.
To get the first element I tried:
{{ $firstTab := index .Params.limits_section.tabs 0 }}
but I get the error:
error calling index: index of untyped nil

The following suggested solutions don’t solve this issue:

When I print the contents of .Params.limits_section.tabs I get [map[...] map[...]] and based on the godocs:

Each indexed item must be a map, slice, or array.

So, I don’t understand why this doesn’t work.
Thanks for the support!

2

You may have content that does not have that front matter param set, so for those cases you are calling index on nil. Try it inside a with (or test if isset):

{{ with .Params.limits_section.tabs }}
  {{ $firstTab := index . 0 }}
  {{ $firstTab }}
{{ end }}
3

What does that mean exactly? My content is an array, as seen in the output of .Params.limits_section.tabs.

I tried your snippet and it works, but then I cannot reference the $firstTab variable outside of the with block. I would have to use Scratch or something to accomplish that.

For a simple operation as fetching the first element of an array, I find this process quite cumbersome…

In other words, there is really no single line statement that will assign the first item of the array to a variable?

4

By ‘content’ I meant your content files, i.e. your .md files.

I am assuming here that you put this chunk

limits_section: 
  title: Foo bar 
  tabs: 
    - title: Foo bar 
      foo: bar 
    - title: Bar foo 
    - foo: bar

into the front matter (Front matter | Hugo) of your content / .md file.

The error may occur when not all .md files have that front matter parameter included. For example if one file does not have limits_section defined, or has it but not tabs.

2 Likes
5

You were right. I had 2 more markdown files using the same template, but the specific content was missing. Thanks!