Module: MetaHash

Defined in:
lib/metahash.rb,
lib/metahash/version.rb

Constant Summary collapse

VERSION = 
"1.0.3"

Instance Method Summary collapse

Instance Method Details

#has_metadata(serialized_field = "metadata", serializer: JSON) ⇒ Object

When an active record object is loaded, convert to Metadata. If for whatever reason we lose this Metadata class, we can read the hash by creating class Metadata < Hash; end

Parameters:

  • serialized_field (Symbol) (defaults to: "metadata") —

    name of the field to convert to Metadata



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# File 'lib/metahash.rb', line 13

def has_metadata(serialized_field = "metadata", serializer: JSON)
  # tell Active Record that the field is going to be JSON
  # serialized, because JSON > YAML
  serialize serialized_field, serializer

  after_initialize do |record|
    # first check the type of the field
    # proceed if hash, abort if Metadata
    if record.has_attribute?(serialized_field)
      if [Hash, NilClass].include?(record.send(serialized_field).class)
        # alias the old method / field
        backup_name = "#{serialized_field}_original".to_sym
        # alias_method backup_name, serialized_field
        record.define_singleton_method backup_name, record.method(serialized_field)
        # name the metadata accessor the same as the original field
        # rails should automatically serialize this on save
        initial_value = record.send(backup_name) || {}
        record.send("#{serialized_field}=", Metadata.new(initial_value))
      end
    end
  end


  # create a before_save hook to store a pure Hash in the DB
  before_save do |record|
    @temp_metadata = record.send(serialized_field)
    record.send("#{serialized_field}=", @temp_metadata.to_hash) if @temp_metadata
  end

  # restore the metadata to the field
  after_save do |record|
    record.send("#{serialized_field}=", @temp_metadata) if @temp_metadata
  end

end