Rails：Grape API - NameError：未初始化的常量API

Question

I am currently learning how to use Rails. I followed the tutorial on this site: http://funonrails.com/2014/03/building-restful-api-using-grape-in-rails/

I put my files not in the lib folder, but in the app folder and edited the application.rb as told in the tutorial. The rest of the code is the same as in the tutorial.

I completed it up until the custom error formatter, but if I start the Rails server to test everything I get the following error:

                Exiting
E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config/routes.rb:3:in `block in <top (required)>': uninitialized constant API (NameError)
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.8/lib/action_dispatch/routing/route_set.rb:337:in `instance_exec'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.8/lib/action_dispatch/routing/route_set.rb:337:in `eval_block'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/actionpack-4.1.8/lib/action_dispatch/routing/route_set.rb:315:in `draw'
    from E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config/routes.rb:1:in `<top (required)>'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application/routes_reloader.rb:40:in `block in load_paths'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application/routes_reloader.rb:40:in `each'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application/routes_reloader.rb:40:in `load_paths'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application/routes_reloader.rb:16:in `reload!'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application/routes_reloader.rb:26:in `block in updater'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.8/lib/active_support/file_update_checker.rb:75:in `call'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/activesupport-4.1.8/lib/active_support/file_update_checker.rb:75:in `execute'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application/routes_reloader.rb:27:in `updater'
    from C:in `execute_if_updated'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application/finisher.rb:71:in `block in <module:Finisher>'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/initializable.rb:30:in `instance_exec'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/initializable.rb:30:in `run'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/initializable.rb:55:in `block in run_initializers'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:226:in `block in tsort_each'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:348:in `block (2 levels) in each_strongly_connected_component'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:427:in `each_strongly_connected_component_from'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:347:in `block in each_strongly_connected_component'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `each'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `call'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:345:in `each_strongly_connected_component'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:224:in `tsort_each'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/2.1.0/tsort.rb:205:in `tsort_each'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/initializable.rb:54:in `run_initializers'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/application.rb:300:in `initialize!'
    from E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config/environment.rb:5:in `<top (required)>'
    from E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config.ru:3:in `require'
    from E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config.ru:3:in `block in <main>'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `instance_eval'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:55:in `initialize'
    from E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config.ru:in `new'
    from E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config.ru:in `<main>'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `eval'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:49:in `new_from_string'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/builder.rb:40:in `parse_file'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/server.rb:277:in `build_app_and_options_from_config'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/server.rb:199:in `app'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands/server.rb:50:in `app'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/rack-1.5.2/lib/rack/server.rb:314:in `wrapped_app'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands/server.rb:130:in `log_to_stdout'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands/server.rb:67:in `start'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands/commands_tasks.rb:81:in `block in server'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands/commands_tasks.rb:76:in `tap'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands/commands_tasks.rb:76:in `server'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands/commands_tasks.rb:40:in `run_command!'
    from C:/RailsInstaller/Ruby2.1.0/lib/ruby/gems/2.1.0/gems/railties-4.1.8/lib/rails/commands.rb:17:in `<top (required)>'
    from bin/rails:4:in `require'
    from bin/rails:4:in `<main>'

If I don't start the server but call rake routes I get the following error:

rake aborted!
NameError: uninitialized constant API
E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config/routes.rb:3:in `block in <top (required)>'
E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config/routes.rb:1:in `<top (required)>'
C:in `execute_if_updated'
E:/Users/Robert/Documents/Rubymine Projects/WarframeApi/config/environment.rb:5:in `<top (required)>'
Tasks: TOP => routes => environment
(See full trace by running task with --trace)

Suggestions?

---

Edits below

Application.rb

require File.expand_path('../boot', __FILE__)

require 'rails/all'

# Require the gems listed in Gemfile, including any gems
# you've limited to :test, :development, or :production.
Bundler.require(*Rails.groups)

module WarframeApi
  class Application < Rails::Application

    # Api load config
    config.paths.add "app/api", glob: "**/*.rb"
    config.autoload_paths += Dir["#{Rails.root}/app/api/*"]
  end
end

Routes.rb

Rails.application.routes.draw do
    mount API::Root => '/'
end

The api files are located in the ./app/api (as suggested as alternative location in the tutorial). Here is the file structure for completeness:

• app
  • api
    • root.rb
    • v1
      • authors.rb
      • posts.rb
      • root.rb

Answer 1

Change your root.rb into this:

class Root < Grape::API
  prefix 'api'
  mount V1::Root
  # mount V2::Root (next version)
end

Or , change your directory structure into this:

app > api > api > root.rb

Rails is looking for api folder as you are using module API . But you have already auto loaded api folder in application.rb , so you need another api folder if you keep your root.rb as it is.

Answer 2

I solved this by changing in the config/routes.rb:

mount V1::Root => "/"

to..

mount Root => "/api"

Answer 3

You just need create another directory structure

• app

  • api

    • api

      • v1

        • authors.rb
        • posts.rb
        • root.rb

      • root.rb