Sort folders by newest post in folders

[lucaschulz.xyz]

Within a list page at https://domain.com/university I list all the modules I participate in.
The basic file hierarchy looks something like that:

content/
├── about.md
└── university
    ├── 2101-mathematik-1
    │   ├── 07-10-2021.md
    │   └── _index.md
    ├── 2102-einfuehrung-in-die-informatik-1
    │   └── _index.md
    ├── 2103-digital-business
    │   ├── 08-10-2021.md
    │   └── _index.md
    ├── 2104-mathematik-3-stochastik-statistik
    │   └── _index.md
    └── _index.md

I want to sort the subfolders under university/ by the newest post appearing in them. If a new post is added to a folder currently on the bottom of the page, it should move to the top.

Currently I use this code snipped within layouts/section/university.html:

{{ define "main" }}
  <h1 class="page-title">{{ .Title }}</h1>
  
    {{ range (site.GetPage "university").Sections }} <!-- .ByDate.Reverse -->
      <ul>
        {{ range .Pages}}
          <li><a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a></li>
        {{ end }}
      </ul>
    {{ end }}
{{ end }}

This currently just sorts the folders by name.

I cannot just change

{{ range (site.GetPage "university").Sections }}

to

{{ range (site.GetPage "university").Sections.ByDate.Reverse }}

as this refers back to the folder, not the posts within them.

If someone got any idea, I would be glad to hear it!

You can have a look how it looks in action on: https://lucaschulz.xyz/university

[jmooring]

It sounds like you want sort the sections by the date of the most recent post within each section. Is that correct?

[lucaschulz.xyz]

Hi jmooring,

thanks for your answer! Yes, that’s the plan.

edit: to be completely clear: The sections should be sorted by the date, posts in them were created.

[jmooring]

{{/*
Build slice of maps, one map for each section. Each map contains three
items:
- dateOfNewestPage: The date of the newest page within the section
- page: The section's page object (to access section .Title, etc.)
- pages: A collection of the pages within the section
*/}}

{{ $sections := slice }}
{{ range (site.GetPage "university").Sections }}
  {{ $dateOfNewestPage := (index .Pages.ByDate.Reverse 0).Date }}
  {{ $sections = $sections | append (dict "dateOfNewestPage" $dateOfNewestPage "page" . "pages" .Pages) }}
{{ end }}

{{ range sort $sections "dateOfNewestPage" "desc" }}
  <h2>{{ .page.Title }}</h2> {{/* .page is the current section page */}}
  <ul>
    {{ range .pages.ByDate.Reverse }} {{/* .pages is the collection of pages within the current section */}}
      <li><a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a></li>
    {{ end }}
  </ul>
{{ end }}

[lucaschulz.xyz]

Wow. Thank you so much for even commenting on what your example code does. It works incredible well. I will push a commit in a few minutes! Have a nice day, @jmooring , you helped me out!