I have a Model with :birthday attribute and I want to filter out those dates by month specified in the form (ActiveAdmin's DSL :select).
This is an example of simple scope that extract only the month of birthday's date. Maybe can help:
scope :birthday_month, where('extract(month from birthday) = ?', Date.today.month)
Here is a solution:
On my Active Admin resource (app/admin/employees.rb) I put:
filter :month, :as => :select, :collection => (1..12)
And on my Model (app/models/employee.rb):
scope :month_eq, lambda{ |month| where("strftime('%m', birthday) + 0 = ?", month.to_i) }
search_methods :month_eq
This approach define '_eq' scope method (MetaSearch) and turn it avaible through search_methods :month_eq
(MetaSearch too).
NOTE:
If you aren't using sqlite, maybe you'll desire to use where('extract(month from birthday) = ?', month.to_i)
instead.