Adding Input from Multi Select Box and converting to a string a store it in a single column in a database - Rails

model.rb

 	def days=(value)
    	return super value.reject!(&:blank?).join(", ") if value.is_a?(Array)
    	super
  	end

view.html.erb

<%= form.label :days %>
<%= form.select :days, ['Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday', 'Sunday'], {}, { :multiple => true, :size => 7 } %>