_form.html.haml

# /app/views/spina/admin/structure_partables/icons/_form.html.haml
.horizontal-form-label
  = f.object.title
.horizontal-form-content
  = f.fields_for :page_partable, f.object.page_partable do |ff|
    = ff.text_field :content, class: 'icon-picker', value: 'fa-anchor'

create_spina_icons.rb

# db/migrate/create_spina_icons.rb
class CreateSpinaIcons < ActiveRecord::Migration[5.0]
  def change
    create_table :spina_icons do |t|
      t.string :content
      t.timestamps
    end
  end
end

default.rb

# config/initializers/themes/default.rb

::Spina::Theme.register do |theme|

  theme.name = 'default'
  theme.title = 'Default Theme'

  theme.page_parts = [{
    name:           'text',
    title:          'Text',
    partable_type:  'Spina::Text'
  },
  {
    name:           'side_image',
    title:          'Side Image',
    partable_type:  'Spina::Photo'
  },
  {
    name:           'structure_list',
    title:          'Structure',
    partable_type:  'Spina::Structure'
  }]

  theme.structures = [{
    name: 'structure_list',
    structure_parts: [{
      name:           'title',
      title:          'Title',
      partable_type:  'Spina::Line'
    },
    {
      name:           'icon_picker',
      title:          'Icon',
      partable_type:  'Spina::Icon'
    },
    {
      name:           'description',
      title:          'Description',
      partable_type:  'Spina::Text'
    }]
  }]

  theme.layout_parts = [{
     name:           'brand_color',
     title:          'Brand Color',
     partable_type:  'Spina::Color'
   }]

  theme.view_templates = [{
    name:       'homepage',
    title:      'Homepage',
    page_parts: ['text']
  },
  {
    name: 'show',
    title:        'Default',
    description:  'A simple page',
    usage:        'Use for your content',
    page_parts:   ['side_image', 'text']
  },
  {
    name: 'list',
    title:        'List',
    description:  'A simple page',
    usage:        'Use for listing content',
    page_parts:   ['text', 'structure_list']
  }]

  theme.custom_pages = [{
    name:           'homepage',
    title:          'Homepage',
    deletable:      false,
    view_template:  'homepage'
  }]

end

icon.rb

# models/spina/icon.rb
module Spina
  class Icon < ApplicationRecord
    translates :content

    has_many :page_parts, as: :page_partable
    has_many :layout_parts, as: :layout_partable
    has_many :structure_parts, as: :structure_partable
  end
end