Creating a custom field formatter

Field formatters define the way in which a field type will be presented. These formatters return the render array information to be processed by the theming layer. Field formatters are configured on the display mode interfaces.

In this recipe, we will create a formatter for the field created in the Creating a custom field type recipe in this chapter. The field formatter will display the first and last name values inline, as a full name.

Getting ready

This recipe provides a field formatter for the field type created in the previous recipe, Creating a custom field type.

How to do it…

1. First, we need to create the src/Plugin/Field/FieldFormatter directory in the module’s directory. The Field module discovers field formatters in the Plugin\Field\FieldFormatter namespace:

   mkdir -p src/Plugin/Field/FieldFormatter

2. Create a RealNameFormatter.php file in the newly created directory so that we can define the RealNameFormatter...