GridField_ExtraFields

Easily manage many_many_extraFields when adding objects to a ManyManyList via a GridField.

TODO:

Create matching GridField_FormAction, GridFieldDataColumns, and/or GridFieldConfig, to modify extra fields when objects have already been linked to the Foreign Key, as well as an injector to use the new classes by default.

Usage:

Currently, all implementations need to be done manually on a per class basis.

public function getCMSFields() {
    $fields = parent::getCMSFields();
    
    // Get ManyMany-RelationEditor-GridField from standard scaffold implementation.
    if ( ( $gridField = $fields->fieldByName( 'Root.RelationName.RelationName' ) ) ) {
        // Determine if it has a ManyManyList and collect the extraFields (optional)
        if ( $gridField->getList()->hasMethod( 'getExtraFields' ) && ( $extraFields = array_keys( $gridField->getList()->getExtraFields() ) ) ) {
            $config = $gridField->getConfig();
            // Remove existing implementation of GridFieldAddExistingAutocompleter (optional, but pointless to keep it)
            $config->removeComponentsByType( 'GridFieldAddExistingAutocompleter' );
            // Replace with new GridFieldAddExistingAutocompleterExtra class with same constructor
            $config->addComponent( new \GridFieldAddExistingAutocompleterExtra( 'buttons-before-right' ) );
            // Update Table Columns to display many_many_extraFields values (oprional).
            $config->getComponentByType( 'GridFieldDataColumns' )
                ->setDisplayFields(
                    singleton( $this-getRelationClass( 'RelationName') )->summaryFields()
                        // You can either use $extraFields to add extra columns
                        + array_combine( $extraFields, $extraFields )
                        // Or you can set your own labels, for instance when $this belongs to the other object
                        + array( 'Value' => $this->Title )
                );
            // Update Item Detail Form to display Extra Fields for Many Many relationships (optional or in contrast/addition to using other classes)
            $config->getComponentByType( 'GridFieldDetailForm' )
                ->setItemRequestClass( 'GridFieldDetailFormExtra_ItemRequest' );
        }
    }
    
    return $fields;
}