Form delegate

Form delegate is a better alternative for entity form alter hooks. It provides a type of plugin, form delegates, which can alter all three methods of entity forms, by this making code better structured.

The module currently provides plugins to alter entity forms only. It is planned to be usable for all types of forms.

This module is provided solely for developers and has no use for end users as is. The documentation below assumes you have a basic knowledge and experience with the core FORM API.

Features

• altering based on entity / bundle / operation / form display mode
• direct access to the form entity
• easy alteration prioritization: no more hook definition alters
• form display mode selection based on context
• possibility for prevention of base submit execution

Requirements / Configuration

The module doesn't require or provide any configuration. Also there are no third party dependencies. The only thing needed to make use of this module is entities.

Getting started

First and foremost you should read through the annotation of the plugin (scr/Annotation/EntityFormDelegate.php). After that you can start implementing plugins under src/Plugin/Form, as an example for the node article content type.

Form display modes

The module provides an event called EntityFormInitEvent which is dispatched when the form is initializing. At this stage it can be selected which display mode a form should use. In certain cases it is useful to present the same form in multiple view modes, for example an account editing form in different ways to the admins and the other users. In this case create your view modes and implement the event subscriber to select the form display mode depending on user role.

Multi-step forms

With entities and form display modes combined with the form delegates it is possible to create multi-step forms. For each step before the final step you can set the delegate to prevent the original submit. Then in each non last step`s submit you should change the display mode on the form object obtained from the from state and set the form state to be rebuilt. This way values get stored on the form state, the form is rebuilt, but with different fields shown / different widgets.

Example delegate plugin in repo README.