Contextual Filters in Views

Editor's Note: The following was written for Drupal 7, but should work as described under Drupal 9.  The one main difference is that Drupal 9 does not have a "master" view, but you could have "block" or other types of views.  Just make sure you're editing the view to which you want to apply a contextual filter.

Contextual filters in Views are powerful, but getting them to work perfectly can be a nightmare. This will hopefully save some people from the headaches I had.

My goal was to have a News page that could easily be filtered to only have specific stories. I started with:

• A Taxonomy vocabulary called "Keywords"
• A "News Story" content type
• A field named "Keywords" in the News Story that is a Term Reference type linked to the Keywords taxonomy

Our news stories are imported from Mercury, and the keywords are automatically imported into the Taxonomy vocabulary.

The goal is to have a page that lists all our news stories at example.gatech.edu/news.  A simple view can handle that easily. With a correctly configured contextual filter, we can add a taxonomy term to the end of the URL, and the view will automatically filter itself down to just the stories tagged with a term. Basically:

• example.gatech.edu/news will list all news stories
• example.gatech.edu/news/robotics will list all news stories with the keyword "robotics"
• example.gatech.edu/news/music will list all news stories with the keyword "music"

Neat, right? The problem is, contextual filters can be a nightmare to set perfectly.

Part 1: Create the Basic View

1. Create a new view at Structure -> Views -> Add. We set ours to show content of type News, sorted newest first.

2. Make sure the "Create a page" box is checked, give it a URL, and set the display format to something simple like unformatted list of linked titles.

3. Save the view and head to the URL to make sure it works. Good? Let's head back and edit that view.

Part 2:  Make the View Advanced!

Make sure you are using the Page display, not the master. Usually when something isn't working, it's because I was not editing the page view.

1. Open the Advanced menu on the right if it isn't already.

2. Select Add next to Contextual filters.

3. Check Content: Has taxonomy term ID in the pop-up and Apply.

On the next page, under "When the filter value is NOT in the URL:"

This controls what the view does when there's nothing added to the end of the view's URL - i.e., in our case, what will show at http://example.gatech.edu/news.  The options include:

• Display all results for the specified field - Shows everything that matches the view's base filter. This is what makes our default news page show all stories.
• Provide default value - Lets you chose a default tag if you want a subset shown.
• Show "Page not found."
• Display a summary.
• Display contents of "No results found."
• Display "Access Denied."

The next section is "When the filter value IS in the URL or a default is provided:"  We used two options:

• Override title - this lets you change the default title. We entered "News stories tagged with %1", which will take the term in the URL and substitute it for the %1. So if you are on example.gatech.edu/news/music, the title will be "News stories tagged with music."
• Specify validation criteria - this is the tricky part. Check this, then:
  • Set Validator to "taxonomy term."
  • Select the "Keywords" vocabulary.
  • Set Filter value type to "Term name converted to Term ID."
  • Check "Transform dashes in URL to spaces in term name filter values."
  • Set Action to take if filter value does not validate to "Display a summary."

Finally, save the filter, then save the view.