ruby on rails - select_day/year/month preset value -

how can preserve value of select_day after validation error? can set default value this:

f.select_day 1, {prefix: 'user[birthdate]'} 

but can't set value model:

f.select_day :birthdate, {prefix: 'user[birthdate]'} 

error:

actionview::template::error (undefined method `day' :birthdate:symbol) 

is possible or need , set value params manually?
model:

class user   include activemodel::model   include activerecord::attributeassignment   attr_accessor :birthdate   def self.build(request, params = {})     u = self.new     u.assign_attributes(params)     u   end end 

controller:

def new   @user = user.new end  def create   @user = user.build(params[:user]) end 

view:

= form_for @user |f|   f.select_day 1, {prefix: 'user[birthdate]'}   f.select_month 1, {prefix: 'user[birthdate]'}   f.select_year 1990, {prefix: 'user[birthdate]'} 

if check documentation select_day (and _month , _year) you'll see methods normally accept date first parameter. accept integer you've chosen decidedly alternate implementation.

be may, i'd suggest couple of small changes. first, i'd consider setting default birthdate user class along these lines.

class user   attr_accessor :birthdate    def initialize()     @birthdate = date.new 1990, 1, 1     super   end    ... end 

then forms can make use of user#birthdate accessor in both new , edit views.

= form_for @user |f|   = f.select_day @user.birthdate, prefix: 'user[birthdate]'   = f.select_month @user.birthdate, prefix: 'user[birthdate]'   = f.select_year @user.birthdate, prefix: 'user[birthdate]'