Ruby convert Object to Hash (and read hash to attributes in case of AR objects)

object_to_hash.rb

module ObjectExtension
  # For any object...
  def to_hash
    hash = {}
    instance_variables.each {|var| hash[var.to_s.delete("@")] = instance_variable_get(var) }
    hash
  end
  
  ##
  # Update all attributes with values from a hash. Only update existing attributes.
  # NOTICE: The attributes expected must be defined in attr_accesor.
  # A safer variant is to define attributes in an array and substitute methods.include? 
  # with attributes.include?. 
  #
  # ```
  # attributes = %i{attr1 attr2 attr3} # This automatically exists in ActiveRecord
  # attr_accessor *attributes
  # ```
  #
  # @param [Hash] attr_values
  def update_from_hash(attr_values)
    filtered_attributes = attr_values.filter { |k, v| methods.include?(k.to_sym)}
    assign_attributes(filtered_attributes)
  end
  
end

module ActiveRecordExtension
  # For ActiveRecord objects...
  def to_hash
    hash = {}
    self.attributes.each { |k,v| hash[k] = v }
    hash
  end
  
  ##
  # Update all attributes with values from a hash. Only update existing attributes.
  # @param [Hash] attr_values
  def update_from_hash(attr_values)
    filtered_attributes = attr_values.filter { |k, v| attributes.key?(k)}
    assign_attributes(filtered_attributes)
  end

end

Learned from:

• Answer https://stackoverflow.com/a/5030763/2100126 by @nashby.
• Answer https://stackoverflow.com/a/6472624/2100126 by @akinom.
• "Update from hash" by @nilsandrey.

• Included update_from_hash for non AR code.
• Added tip on comments based on an answer of a non directly related question in SO provided by @davetapley.