Drupal

I had to update a Drupal 7 site recently and needed to change the field keys of a list field to be different values. This wasn't possible from within Drupal as it does a pre-check to make sure that the key doesn't already exist. If it finds any values present in the database with that key then it will reject the change. This is absolutely correct but causes a little bit of an issue when you need to update these values.

The solution to this is to alter both the field definition and the field data via directly altering them in the database. The following function provides a neat little way of doing this to a field by just passing in the field name and what the key values need to change to.

The European DrupalCon was held in Dublin from 26th - 30th September and I went along with a couple of colleagues to learn a few things about Drupal. I have been back from the conference for a few days now, and I wanted to write down some of the highlights of the conference in a blog post. There is a lot going on at DrupalCon and with 2000+ people, 3 full days of sessions, 2 tutorial days, multiple parties and over 10,000 cups of coffee consumed there is too much to write about here. So this will be a few random highlights and stand out moments of the conference.

I was recently asked to implement a feature on a Drupal site where all nodes of a certain type would redirect to a main listing page if that node had been unpublished. The problem in doing this is that if a post is unpublished then Drupal will issue an access denied response quite early on in the boot process. When the menu item is loaded it goes through an access callback which sees that the post is unpublished and issues an access denied before anything else can happen. So in this situation you can't use things like Rules to redirect users as the rule is never triggered.

The solution was to use hook_menu_alter() to change the access callback parameter of the node page. We are essentially replacing the normal access callback of node_access() with our own version.

To get the currently selected language on a Drupal 8 site you need to run the following.

When creating re-usable theme templates in Drupal 8 it's quite easy to include that template by using the following snippet.

{% include directory ~ '/templates/parts/footer.html.twig' %}

This assumes that your footer.html.twig template file is kept in the same theme as the template you are working on. It's also good practice to add the template part to a directory called 'parts' or 'components' to separate them from the normal Drupal templates.

When overriding theme functions in Drupal 7 you would normally copy the theme function into the template.php and alter it to suit your needs. This isn't always convenient though, especially if you are trying to abstract functionality into modules and not have code in your theme layer that is reliant on module code. If you add theme override functions to your module files then they won't do anything as Drupal isn't looking for them there and won't pick them up.

It is possible to alter the theme registry in order to get Drupal to pick up your theme functions from your module code. This helps collect together code that performs a certain task and allows you to deploy theme alterations along with module updates.

Or, how you can render a Drupal page with an entirely different template.

I recently had a requirement where I needed to get Drupal to render a single page of HTML that was entirely separate from the normal page layout of a site. This was actually part of an API callback, but this got me involved in looking at how delivery callbacks work in Drupal 7. It isn't necessary to create a new theme just for the job of rendering a single page with some custom HTML, especially as Drupal has mechanisms to provide this built in.

There are a few ways in which you can create complex node access systems. Modules like Taxonomy Access Control and Node Access will allow you to restrict node access in different ways, and work very well for setting up taxonomy or role based access control. There are a few edge cases where you need to restrict access to a node based on some arbitrary conditions like the age of the user or the contents of a field. This is where the build in Drupal access control mechanisms come into play. They do take a little bit of effort to get around how they work, but I hope to enlighten in this post.

Basic HTTP authentication is a simple authentication mechanism that is used to prevent access to a site or directory on a server. It is by no means the most secure authentication mechanism but it is commonly used on staging sites in order to prevent unwanted access. This is a good way of preventing search engine bots from spidering the staging site, which is undesirable as it can cause staging site pages appearing in search engines results.

The usual route to set this up is to create a .htaccess that sets up the authentication and references a .htpasswd file to create the username and password details. This can mean editing the .htaccess file in order to setup the password correctly. Unfortunately, this creates a .htaccess file that shouldn't be added to the repository as it would mean that the live site would also be password protected when the code is deployed.

When generating markup in Drupal you'll often want to store the output in a cache instead of regenerating it every time. This is especially important for potentially expensive rendering tasks that don't change between page requests. Drupal 7 comes with a cache system that can be taken advantage of with the cache_get() and cache_set() functions. There is also a third function called drupal_static() that also fills in gaps between these two functions.