activeadmin.md

+# ActiveAdmin
+
+## Custom Filters
+
+Defining custom filters in activeadmin is a simple task but the details on how to implement them are not easy to find on web. Here is an example of how to define them.
+
+First you have to define a new ransacker in the model you want to apply the filter on:
+
+ransacker :country,
+    formatter: proc { |country|
+      results = Order.find_by_country(country).map(&:id)
+      results = results.present? ? results : nil
+    }, splat_params: true do |parent|
+    parent.table[:id]
+  end
+
+Then you have to define the actual code that will do the filter:
+
+def self.find_by_country(country_name)
+    Order.where(
+      "shipping_address @> hstore(:key, :value)",
+      key: "country",
+      value: country_name
+    )
+  end
+
+[Source](https://git.altum.com.br/gocase/gocase-factory/blob/develop/app/models/order.rb)
+
+Lastly you can register the filter using activeadmin (usually we do this in the index page implementation):
+
+filter :country_in, as: :select, collection: Country::ALL
+
+[Source](https://git.altum.com.br/gocase/gocase-factory/blob/develop/app/ui/go_logistics/order/index.rb)
+
+## References
+
+[ActiveAdmin Filters with Ransack](https://cavewall.jaguardesignstudio.com/2014/05/01/activeadmin-filters-with-ransack/)
+
+
+