How can i interpolate ivars into Rails i18n strings during validation?

Suppose I have a model class like this:

class Shoebox < ActiveRecord::Base
  validates_inclusion_of :description, :in => ["small", "medium"],
    :message => I18n.t("activerecord.errors.models.shoebox.with_name",
                     :name => name)
end

And some ya开发者_开发问答ml:

en:
 activerecord:
  errors:
   models:
    shoebox:
     with_name: "the description of %{name} is not in the approved list"

And I create a new Shoebox:

   s = Shoebox.new(:description => "large", :name => "Bob")
   s.valid?

But when I look at the error (s.errors.first.message), I see:

"the description of Shoebox is not in the approved list"

and not:

"the description of Bob is not in the approved list"

I've tried :name => name, :name => :name, :name => lambda{name}, :name => lambda{:name}.

I've tried creating a helper method

 def shoebox_name
   name
 end

And passing :name => shoebox_name, :name => :shoebox_name, :name => lambda{shoebox_name} and :name => lambda {:shoebox_name}.

How can I get the ivar value for name to be interpolated into the string?

Try removing the message option in the validation, and change your yaml to be:

en:
 activerecord:
  errors:
   models:
    shoebox:
     description:
       inclusion: "the description of %{name} is not in the approved list"

See http://guides.rubyonrails.org/i18n.html#translations-for-active-record-models for more details

You can use a custom validation method to achieve what you are trying to do. All the columns are available in the custom validator:

validate :description_in

def description_in
  if !(["small", "medium"].include?(description))
    errors.add(:base, "The description of #{name} is not in the approved list")
  end
end

PS: After a lot of googling around, I realized that it was much easier to implement a custom validator than search around.