All page content is stored in a single JSONB-column in the database. Spina uses the
attr_json gem to work with these nested json objects. All default parts are
AttrJson::Model objects. Follow the steps below to create your own custom part.
Let's imagine our app contains a movie database. We'd like to add a part to select one of the movies in our collection. First we need to create the object that can be stored as page content.
# app/models/spina/parts/movie.rb module Spina module Parts class Movie < Base attr_json :movie_id, :integer def content Movie.find_by(id: movie_id) end end end end
In this simplified example we make the content method do a query and return a Movie record. Beware of N+1 queries if you go this route. Generally, the more you store directly in JSON, the better your performance.
ActiveRecord::RecordNotFound Exception will be displayed as 404, which may be happening when using
Movie.find (movie_id) if movie_id is nil or not found in Database. You should consider using
Movie.find_by (id: movie_id), which will not throw an Error but return nil if movie_id is nil or not found in Database.
<!-- app/views/spina/admin/parts/movies/_form.html.erb --> <div class="mt-6"> <label class="block text-sm leading-5 font-medium text-gray-700"><%= f.object.title %></label> <div class="mt-1"> <%= f.select :movie_id, Movie.all.pluck(:name, :id) %> </div> </div>
In an initializer, register your newly created part so you can use it in your theme:
Rails.application.reloader.to_prepare do Spina::Part.register(Spina::Parts::Movie) end
<p>Film Director: <%= content(:movie)[:director] %></p>
Of course, this is a very simple example. You can store a lot this way. You can take a look at the existing parts in Spina for inspiration. If you want to learn more, you can also take a look at the attr_json readme.