Checking day against date in Rails 3 using simple_form -

what's best way check date against day in rails?

i have register registers take place on days, , want restrict selectable dates match days i.e. if register set monday 15:00, date selection should provide dates monday i.e. 1st april 2013, 8th april 2013, 15th april 2013 etc.

here screenshot of current register looks like:

my form uses simple_form gem, , has following simple input:

<%= f.input :date %> 

edit: here model, requested cthulhu

class register < activerecord::base   has_many :student_registers   has_many :students, :through => :student_registers   belongs_to :event   attr_accessible :date, :student_ids, :module_class_id, :event_id end 

date class has plenty of useful methods, like

>> d = date.today => fri, 05 apr 2013 >> d.monday? => false >> d.friday? => true >> d.wday => 5 

it should enough write validation method:

class register < activerecord::base   validates_each :date |record, attr, value|     record.errors.add(attr, "must #{event.day}") unless value.wday == date.parse(event.day).wday # assume 'event.day' holds weekday string, e.g. 'monday'   end end