Question

When my Rails uniqueness validation fails, I would like to display the duplicate record using a partial in the form view when the user is sent back.

How do I accomplish this? Right now I only know how to alter the error message that is displayed.

Answer 1

There isn’t a built-in way to do this in Rails, and there’s probably a dozen ways to do it. Here’s one approach, while not elegant, should get you what you want.

1) Check if there’s a uniqueness validation error. Unfortunately there isn’t an easy way to do this, so you’ll have to check the name of the error in your controller. If there’s an error, search for the existing record, and store it in an instance variable:

def create
  @new_model = Model.new(params[:model])

  if @new_model.save
    # success...
  else
    if @new_model.errors[:field].index("has already been taken")
      @existing_record = Model.where(field: model.field).first
    end

    render :new
  end
end

2) Render the existing record in a partial in your view

<%= render partial: 'partial_name', locals: {existing_record: @existing_record} %>