This lesson is a short one but it covers an important topic, multi-value fields. Almost any field in Drupal can be configured to support more than one value being entered for a single field. Our teams entityreference field is a good example of this, a player could have played for one or more team over the course of their career. This lesson will look at two different ways to map multiple values for a single field.
First we'll look at doing it in a callback method where we perform an additional query and then use the values returned by that query. And second we'll look at using the field mapping's separator method to take a column in a source row that has multiple values separated by a comma and import them as individual field values.