rails_admin get the current entity and display custom enum - ruby-on-rails-4

Question

I'm trying to customize an enum field with something else than only the name.
For example my entity record from database have columns as: name, postal_code, id etc ..
and I would like to have something like this in the dropdown "#{name} #{postal_code}, #{department}
I'm doing this:
field :city, :enum do
enum do
# Here I would like to get the entity from DB in order to have all
# columns to something similar as =>
entity.collect.each { |c| "#{c.name} (#{c.postal_code}), #
{c.department.name}"}
end
end
but I don't know how to get the active records (entity in my example) of the actual value of City entity.
How can I do this?
note: that department belongs to another model who is associated to City

Answer 1

Considering the OP comments i'm going to asume that the model in question has this association defined like this:
belongs_to :city
And the city field itself something like this
rails_admin do
edit do
field :city
end
end
Because this way rails admin will render a select drop down that will allow you to search the cities without loading them all.
After that on the City model you can define the title method, quoting the docs
By default it tries to call "name" or "title" methods on the record in question. If the object responds to neither, then the label will be constructed from the model's classname appended with its database identifier. You can add label methods (or replace the default [:name, :title]) with:
RailsAdmin.config {|c| c.label_methods << :rails_admin_title }
The title method can then be defined
class City < ApplicationRecord
def rails_admin_title
"#{self.name} (#{self.postal_code}), #{self.department.name}"
end
end
In a related issue, you will probably want to configure how rails admin searches for the city, i'll just link to the docs.

Answer 2

You can do it, but you need to define a name and a (stable)value for each select drop down, a simple hash out to do it like this:
field :city, :enum do
enum do
entity = bindings[:object]
City.all.map do |c|
{c.id => "#{c.name} (#{c.postal_code}), #{c.department.name}"}
end
end
end
Im assuming each city has an id, but you can use any value you want to store on that field on your DB.
So your users would see the nice formatted string, but rails admin would post the form with the city id on the city field.