Composition

Reform allows to map multiple models to one form. The complete documentation is here, however, this is how it works.

class AlbumForm < Reform::Form
  include Composition

  property :id,    on: :album
  property :title, on: :album
  property :songs, on: :cd
  property :cd_id, on: :cd, from: :id

  validates :title, presence: true
end

Note that Reform now needs to know about the source of properties. You can configure that by using the on: option.

Composition: Setup

When initializing a composition, you have to pass a hash that contains the composees.

form = AlbumForm.new(album: album, cd: CD.find(1))

The form now hides the fact that it represents more than one model. Accessors for properties are defined directly on the form.

form.title #=> "Greatest Hits"

Composition: Save/Sync

On a composition form, sync will write data back to the composee models. save will additionally call save on all composee models.

When using `#save’ with a block, here’s what the block parameters look like.

form.save do |nested|
  nested #=>
    {
      album:  {
        id:    9,
        title: "Rio"
      },
      cd:     {
        songs: [],
        id: 1
      }
    }
end

The hash is now keyed by composee name with the private property names.

Composition: ActiveModel

With ActiveModel, the form needs to have a main object configured. This is where ActiveModel-methods like #persisted? or ‘#id’ are delegated to. Use ::model to define the main object.

class AlbumForm < Reform::Form
  include Composition

  property :id,    on: :album
  property :title, on: :album
  property :songs, on: :cd
  property :cd_id, on: :cd, from: :id

  model :album # only needed in ActiveModel context.

  validates :title, presence: true
end

Hash Fields

Reform can also handle deeply nested hash fields from serialized hash columns. This is documented here.

Nesting