ruby on rails - default for serialized column in activerecord migration -

so have serialized column :dimensions, , in migration, set field default hash.

i have tried...

create_table :shipping_profiles |t|       t.string      :dimensions_in, :default => {:width => 0, :height => 0, :depth => 0} 

and just

t.string :dimensions_in, :default => hash.new() 

but fields end null. how can set default serialized object field on creation, or @ least make sure serialize attribute hash?

when rails serializes hash save in db, convert yaml can stored string. work in migration, need convert hash yaml...

t.string :dimensions_in, :default => {:width => 0, :height => 0, :depth => 0}.to_yaml 

or, alternatively, set in model after initialization...

class shippingprofile < activerecord::base    after_initialize :set_default_dimensions    private      def set_default_dimensions       self.dimensions_in ||= {:width => 0, :height => 0, :depth => 0}     end  end