Assign a category group to a category field via migration

Question

I am writing a plugin that sets up Craft in a particular way and have created a category field, but can't figure out how to assign a category group to the field, I have the following:

 protected function createCategoriesField() {

        // Get the field group
        $group = (new \craft\db\Query())
            ->select("id")
            ->from("fieldgroups")
            ->where(["name" => "common"])
            ->one();

        // Get the category group
        $catGroup = Craft::$app->categories->getGroupByHandle("categories");


        // Initialize the field
        $field = new \craft\fields\Categories([
            "groupId" => $group["id"],
            "name" => "Categories",
            "handle" => "categories",
            "selectionLabel" => "Select categories",
            "sources" => $catGroup
        ]);

        // Save the field
        return (Craft::$app->getFields()->saveField($field));
    }

It seems sources is the correct setting, but it accepts 'source keys' which I'm unfamiliar with 🤔

Answer 1

Figured it out, the format it expects is 'source' => 'group: <group UID>'

So...

    protected function createCategoriesField() {
        // Get the group
        $group = (new \craft\db\Query())
            ->select("id")
            ->from("fieldgroups")
            ->where(["name" => "common"])
            ->one();

        // Get the category group UID
        $catGroup = Craft::$app->categories->getGroupByHandle("categories")->uid;

        // Initialize the field
        $field = new \craft\fields\Categories([
            "groupId" => $group["id"],
            "name" => "Categories",
            "handle" => "categories",
            "selectionLabel" => "Select categories",
            "source" => "group:" . $catGroup
        ]);

        // Save the field
        return (Craft::$app->getFields()->saveField($field));
    }

This was, and is, going to be a big help with migrations -> https://github.com/markhuot/craftql/blob/master/src/Console/ToolsController.php