formtastic_tristate_radio

https://github.com/sergeypedan/formtastic-tristate-radio

Have 3-state radiobuttons instead of a 2-state checkbox for your Boolean columns which can store NULL. This gem: 1. Provides a custom Formtastic input type `:tristate_radio` which renders 3 radios (“Yes”, “No”, “Unset”) instead of a checkbox (only where you put it). 2. Teaches Rails recognize `"null"` and `"nil"` param values as `nil` 3. Encourages you to add translations for ActiveAdmin “status tag” so that `nil` be correctly translated as “Unset” instead of “False”. Does not change controls, you need to turn it on via `as: :tristate_radio` option.