Rails query parameter with same name as optional path parameter

This is not a very good solution as it violates the RESTful conventions.

In Rails flavor REST GET /resource_name/:id maps to the show route. In the case of get "/items/(:brand)", to: "items#index", as: :items this creates an ambiguity (is the segment an item id or a brand?) when the router matches the requests and the first declared route will win which is hardly desirable.

A better solution is to declare it as a nested resource:

resources :brands, only: [] do
  resources :items, only: [:index], module: :brands
end

    Prefix Verb URI Pattern                       Controller#Action
brand_items GET  /brands/:brand_id/items(.:format) brands/items#index

# app/controllers/brands/items_controller.rb
module Brands
  class ItemsController < ::ApplicationController
    before_action :set_brand

    # GET /brands/:brand_id/items
    def index
      @items = @brand.items
    end

    def set_brand
      @brand = Brand.find(params[:brand_id])
    end
  end
end