Creating View of Distinct Active Taxonomy Terms (browse by category)

Last updated February 4, 2011. Created by RedTop on April 14, 2010.
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1. Introduction

1.1 Background

A list of distinct active taxonomy terms can be useful as it allows visitors to browse content by taxonomy term (categories). Trying to set up such a list using views often results in a list with duplicates. As lots of people seem to hit the same wall when trying to set this up I thought I'd put in the effort of creating this recipe. :)

1.2 Requirements

For this you'll need to have views installed and taxonomy enabled. You should already know how to set up vocabularies and how to categorize content. If not, you may want to read the Taxonomy handbook first.

1.3 Update history

When I first created this recipe I used a method provided by Himerus on his website. After a couple of months a much, much easier way of doing this became available thanks to joel_guesclin and merlinofchaos.

2. Solutions

2.1 Solution using Term View

This solution is easier than the original (advanced solution) recipe found below while still offering the required flexibility to group terms etc. It uses Term View and not Node View thus preventing the duplicates issue.

1) add a new view of view type "term" (not the default "node" option!) by ticking the correct option after clicking 'add view'
2) add the Taxonomy Term to the list of Fields
3) Add a relationship "Taxonomy: Node" and make it obligatory
4) In the basic settings enable the 'distinct' option.
5) Add some filters to narrow the results as needed. (i.e. only nodes from a certain content type)

That's it! This should solve the enormous amount of issues with duplicates. :)

2.2 Original recipe

Below is the original, more difficult and probably less efficient recipe. I kept this for archiving purposes. Maybe it is still useful to some although I do recommend the method described above.

2.2.1 Basic setup

Regardless of whether you go for the basic or advanced solution, make sure you have done the following:

1) add a new view of view type "node"
2) set row style to "Fields"
3) optionally set style to "Grid"
4) though not strictly necessary lots of you will want to add filters to limit the content types and limit to published content.
5) add a field "Taxonomy: Term"

Now, usually the resulting list contains duplicates as the view simply lists the terms of every node that passes the filtercriteria. So if there are two nodes that pass the filter and both have taxonomy term "little green birds", the list would contain two instances of "little green birds".

There's a basic solution and a more advanced solution:

2.2.2 Basic solution

The basic solution, thanks to drupal3008 uses the views "Arguments" section:
1) add an argument for "Taxonomy: Term"
2) Title: %1
3) Action to take: Summary, sorted Ascending
4) Wildcard: All
5) Wildcard Title: All
6) Basic Validation
7) Hide view / Page...
8) Case: Capitalize each word (This is my preference)
9) Case in path: Lower case
10) Transform spaces to dashes (checked)
11) On next option after you add field, select: List

This presents you with a basic list of all active taxonomy terms. However, it strips the possibility to order the terms according to vocabulary and allows little control over the output.

2.2.3 Advanced solution

The advanced solution involves creating a custom module for using hook_views_pre_render:

custom.info

custom.module, copied from himerus' website

1) ... remember to delete the PHP closure tag (get rid of ?>) to comply with Drupal coding standards. It's just used here to enable syntax highlighting.
2) replace"your_view_name" in line 14 to, well, your view name.
3) replace YOUR_FIELD with your field. This can be found by hovering over the field "Taxonomy: Term" we just added and looking at the url which appears in the browsers statusbar. The field name is behind the last slash ("/"). Make sure to keep the double underscore after YOUR_FIELD. It's not a typo.
4) enable the module.

Now, this code may or may not not work straight away. If it doesn't it probably has to do with the naming pattern (i.e. "node_node_data_YOUR_FIELD__term_data_name" and "node_node_data_YOUR_FIELD__term_data_tid" should be different)

To find out what the correct naming pattern is insert this just before line 14:

Run the live preview of the view (On the edit view form) after which there should be a drupal message showing the contents of array $view.

Look for something like:

As you can see, in this case "node_node_data_YOUR_FIELD__term_data_name" has to be replaced with "term_data_name" and "node_node_data_YOUR_FIELD__term_data_tid" has to be replaced with "term_data_tid". This is just an example, but should get you going.

Save the lot and you should have a list of distinct, active taxonomy terms. If so, you can start editing the view to your heart's content. This is really the biggest advantage of the more advanced solution. For example, you could group the list by vocabulary if you are using more than one:

1) add a field "Taxonomy: Vocabulary Name"
2) Edit the field to exclude the field from display as we don't want to display this field, we just want to use the data.
3) optionally, rewrite the output of the field to something like: "Browse by [FIELD]", changing FIELD to the fieldname. You can find the fieldname by hovering over the Taxonomy: Vocabulary name" field. Usually it's "name_1".
4) Edit the settings of the view "Style" (click on the cog behind "Style").
4) select Grouping field: "Taxonomy: Vocabulary name"