Sequel file plugin

gistfile1.rb

require 'pathname'

module Storage
  class Local
    attr_reader :path
    def initialize(path)
      @path = Pathname(path).expand_path
    end

    def [](id)
      Collection.new(id, self)
    end
  end

  class Collection

    def initialize(id, store)
      @id = id.to_s
      @store = store
    end

    def path
      @store.path + @id
    end

    def [](id)
      File.new file_path(id)
    end

    def []=(id, io, mode = 'w')
      File.open(file_path(id), mode) do |f|
        f << io.read(4096) until io.eof?
      end
    end

    def delete(id)
      File.unlink file_path(id) if File.exist? file_path(id)
    end

    private

    def file_path(id)
      FilePath.new(id, self).path
    end
  end

  class FilePath

    def initialize(id, collection)
      @id = id.to_s
      @collection = collection
    end

    def path
      @collection.path + @id
    end
  end
end

module Sequel
  module Plugins
    module File

      def self.configure(model, **options)
        model.instance_variable_set(:@storage, options.fetch(:storage))
        model.plugin :dirty
      end

      module ClassMethods
        def storage
          @storage[table_name]
        end
      end

      module InstanceMethods

        def file
          @file ||= self.class.storage[id] unless new?
        end

        def file=(v)
          will_change_column(:file)
          @file = v
        end

        def after_create
          super
          self.class.storage[id] = file
        end

        def after_update
          super
          self.class.storage[id] = file if column_changed?(:file)
        end

        def after_destroy
          super
          self.class.storage.delete(id)
        end
      end
    end
  end
end

require 'sequel'

DB = Sequel.sqlite

DB.create_table :assets do
  primary_key :id
end

class Asset < Sequel::Model
  plugin :file, storage: Storage::Local.new('~/Desktop/store')
end

require 'stringio'
a = Asset.create(file: StringIO.new('abc'))
a.update(file: StringIO.new('def'))
a.file.rewind
p a.file.read