How do Formtastic decides which table column is used in the `select` options to represent the row?

When you do the following:

form.input :users

And the attribute #users represents a has_many relationship, then Formtastic generates a select field with the user #id and #name, but...

How do Formtastic decides that the #name column is what has to be used?

Why not #email, or #login? Is possible to specify it without having to create the collection manually?

Solution

Well I found my answer, the source comments for the :select tag says the following:

The way on which Formtastic renders the value attribute and content of each <option> tag is customisable through the :member_label and :member_value options. When not provided, we fall back to a list of methods to try on each object such as :to_label, :name and :to_s, which are defined in the configurations collection_label_methods and collection_value_methods.

https://github.com/justinfrench/formtastic/blob/master/lib/formtastic/inputs/select_input.rb