Extracting taxonomies from page frontmatter

support
1

Let’s assume there are taxonomies defined in config.toml like this:

[taxonomies]
    taxonomy(1)             = "taxonomies(1)"
    taxonomy(2)             = "taxonomies(2)"
    taxonomy(3)             = "taxonomies(3)"
    taxonomy(4)             = "taxonomies(4)"
    taxonomy(5)             = "taxonomies(5)"
    taxonomy(6)             = "taxonomies(6)"

and each of them has some terms associated.
Now in a content page we have a frontmatter like this:

+++
date           = "2019-12-31T09:07:05+02:00"
title          = "some interesting page"
description    = "this is awful stuff"
taxonomy(2)    = ["term(21)", "term(24)"]
taxonomy(5)    = ["term(52)", "term(53)"]
+++

In a single page template for that section I want to get the taxonomies and their associated terms used in the particular page which of course is a subset of the taxonomies defined in the config.toml.

So for the page above I want to get that taxonomies 2 and 5 with their terms 21 and 24 or 52 and 53 respectively.

Goal is to do something like:
"More articles in [taxonomy(2)](link-to-taxonomy(2)-list-page) about the subjects [term(21)](link-to-term(21)-list-page) and [term(24)](link-to-term(24)-list-page)"
somewhere on each single page.

I could not figure out how to do that. I only found explanations on how to do some sort of navigation based on all of the taxonomies from the config.toml

2

Have you figured out how to show all the terms in a single taxonomy for a piece of content?

3

not yet.
I’m still trying to start at the beginning: figure out how to find out about the taxonomy itself.

4

Use the samples in the docs and study the themes in the showcase; examples of taxonomy use abound.

5

In the docs I simply can’t find anything that could apply to content pages.
In list pages I simply have

        <ul>
            {{ range $taxonomyname, $taxonomy := .Site.Taxonomies }}
            {{ if ne $taxonomyname "main" }} 
              <li>
                <a href="{{ "/" | relLangURL}}{{ $taxonomyname | urlize }}.html">{{ $taxonomyname | upper }}</a> <!-- "| upper"  oder "| humanize"  -->
              </li>
            {{ end }}
            {{ end }}
        </ul>

to show a list of taxonomies - but in a content page I only want to show the taxonomies assigned to that page.

Further:
This https://gohugo.io/templates/taxonomy-templates/#display-a-single-piece-of-contents-taxonomies skips the first step i need: finding out which taxonomies exist on this page.
The examples assume “tags” or “directors” - but I don’t know that in advance in the template, because that is defined in frontmatter of the respective content page.

6

Meanwhile I’ve come up with the following approach:

  1. range through the site-wide taxonomies as above
  2. check for each of them, if .Param.[taxonomyname] exists and is set on the current content page
  3. if yes => go further with extracting the content of the existing .Param.[taxonomyname] => these should be the needed terms.

But in practice I’m not able to do step 2.
I cannot find a way to do something like isset in other languages (at least not one that I understand).

7

I have a taxonomy called bildbearbeitung in frontmatter with

+++
bildbearbeitung= ["RAW"]
+++

If I do

    {{ if .Params.bildbearbeitung }}
        <p>bildbearbeitung exists</p>
    {{ end }}

Hugo prints out the sentence.
With

    {{ if .Params.foo }}
        <p>bildbearbeitung exists</p>
    {{ end }}

output is empty obviously as there is no such taxonomy.

Now I would like to do this:

<ul>
{{ range $taxonomyname, $taxonomy := .Site.Taxonomies }}
    {{ if .Params.$taxonomyname }} 
        <li>
            <a href="{{ "/" | relLangURL}}{{ $taxonomyname | urlize }}.html">{{ $taxonomyname | upper }}</a> <!-- "| upper"  oder "| humanize"  -->
        </li>
    {{ end }}
{{ end }}
</ul>

but Hugo tells me:

Process: loading templates: “/home/path/to/theme/layouts/partials/pagetax.html:5:1”: parse failed: template: partials/pagetax.html:5: bad character U+0024 ‘$’

So how can I do that if-statement {{ if .Params.$taxonomyname }} (this is the cause fo the error) right?

8

I cannot believe that noone seems to know the correct syntax of concatenating strings in a template :thinking:

I’m still struggling with this.
As mentioned in step 2 I have to check the existance of a frontmatter parameter. This is the taxonomy as described in the first entry of this discussion .

So I still try to set a variable, let’s say $taxcheck as a combined string out of ".Params." and the variable $taxonomyname but I cannot figure out how to do this :confused: .

Next thing then would be to do an if-statement to check if

  • either this concatenated variable exists in the page frontmatter
  • or, if not possible, if this concatenated variable is not empty
9

After reading this https://gohugo.io/templates/introduction/#example-4-if--else again I tried config.toml

[taxonomies]
    foo             = "foos"
    bar             = "bars"
    baz             = "bazs"

frontmatter

+++
date           = "2019-12-31T09:07:05+02:00"
title          = "some interesting page"
description    = "this is awful stuff"
bar            = ["bar1term", "bar2item"]
+++

and this partial

<ul>
{{ range $taxonomyname, $taxonomy := .Site.Taxonomies }}
    {{ if (isset .Params $taxonomyname) }} 
        <li>
            Taxonomy is {{ $taxonomyname }}
        </li>
    {{ else }}
        <li>{{ $taxonomyname | upper }} not found</li>
    {{ end }}
{{ end }}
</ul>

but I always get the “not found” statement - which I would be expecting to be correct for foo and baz taxonomy, but not for bar.

10

I don’t create general use themes that produce taxonomies, so I’m not sure of the exact code I’d use to check.

In my practical case, I generate a layout for each taxonomy as its added to my project, so I can control that aspect. From your original goal, you know what the taxonomies are, to produce the human readable text. That text depends on a human understanding the relationship between the taxonomies.

What you seem to want is a name of the taxonomies used in the front matter of a given piece of content, for it’s own sake (to operate on later). I don’t think many folks have that goal in mind. You know: you set the taxonomies in front matter, how do you not know that they are? :slight_smile:

Anyhow, if you needed to know which taxonomy a piece of content has, you can compare the parameters in the front matter to .Site.Taxonomies, and maybe use intersect to produce your list. Or something. :sunglasses:

Also, sharing a repo to clone to reproduce your work goes a long way.

11

Isn’t the taxonomy name plural, e.g. bars? Yet your front matter taxonomy name is singular.