Question

我是Ruby on Rails的新手。我在这里按照教程Getting Started Ruby on Rails

在创建帖子的过程中，我偶然发现了一个错误，即我的控制器中的PostsController #create中的NoMethodError。我现在很困惑。

这是我在教程中遵循的代码。我在这里犯了一个愚蠢的错误吗？

posts_controller.rb

 class PostsController < ApplicationController

  def new

  end

  def create
    @post = Post.new(post_params)

    @post.save
    redirect_to @post
  end

  def show
    @post = Post.find(params[:id])
  end

  private
  def post_params
    params.require(:post).permit(:title, :text)
  end

end

我的帖子/ new.html.erb

<%= form_for :post, url: posts_path do |f| %>
    <p>
      <%= f.label :title %><br>
      <%= f.text_field :title %>
    </p>

    <p>
      <%= f.label :text %><br>
      <%= f.text_area :text %>
    </p>

    <p>
      <%= f.submit %>
    </p>
<% end %>

的routes.rb

Blog::Application.routes.draw do

  resource :posts
  root to: "welcome#index"

end

模型/ post.rb

class Post < ActiveRecord::Base
end

和堆栈跟踪

actionpack (4.0.0) lib/action_dispatch/routing/polymorphic_routes.rb:129:in `polymorphic_url'
actionpack (4.0.0) lib/action_dispatch/routing/url_for.rb:159:in `url_for'
actionpack (4.0.0) lib/action_controller/metal/redirecting.rb:100:in `_compute_redirect_to_location'
turbolinks (1.3.0) lib/turbolinks.rb:15:in `_compute_redirect_to_location_with_xhr_referer'
actionpack (4.0.0) lib/action_controller/metal/redirecting.rb:70:in `redirect_to'
actionpack (4.0.0) lib/action_controller/metal/flash.rb:40:in `redirect_to'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:61:in `block in redirect_to'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.0.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:60:in `redirect_to'
app/controllers/posts_controller.rb:11:in `create'
actionpack (4.0.0) lib/action_controller/metal/implicit_render.rb:4:in `send_action'
actionpack (4.0.0) lib/abstract_controller/base.rb:189:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/rendering.rb:10:in `process_action'
actionpack (4.0.0) lib/abstract_controller/callbacks.rb:18:in `block in process_action'
activesupport (4.0.0) lib/active_support/callbacks.rb:403:in `_run__506468238__process_action__callbacks'
activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.0) lib/abstract_controller/callbacks.rb:17:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/rescue.rb:29:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:31:in `block in process_action'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `block in instrument'
activesupport (4.0.0) lib/active_support/notifications/instrumenter.rb:20:in `instrument'
activesupport (4.0.0) lib/active_support/notifications.rb:159:in `instrument'
actionpack (4.0.0) lib/action_controller/metal/instrumentation.rb:30:in `process_action'
actionpack (4.0.0) lib/action_controller/metal/params_wrapper.rb:245:in `process_action'
activerecord (4.0.0) lib/active_record/railties/controller_runtime.rb:18:in `process_action'
actionpack (4.0.0) lib/abstract_controller/base.rb:136:in `process'
actionpack (4.0.0) lib/abstract_controller/rendering.rb:44:in `process'
actionpack (4.0.0) lib/action_controller/metal.rb:195:in `dispatch'
actionpack (4.0.0) lib/action_controller/metal/rack_delegation.rb:13:in `dispatch'
actionpack (4.0.0) lib/action_controller/metal.rb:231:in `block in action'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `call'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:80:in `dispatch'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:48:in `call'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:71:in `block in call'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `each'
actionpack (4.0.0) lib/action_dispatch/journey/router.rb:59:in `call'
actionpack (4.0.0) lib/action_dispatch/routing/route_set.rb:655:in `call'
rack (1.5.2) lib/rack/etag.rb:23:in `call'
rack (1.5.2) lib/rack/conditionalget.rb:35:in `call'
rack (1.5.2) lib/rack/head.rb:11:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/params_parser.rb:27:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/flash.rb:241:in `call'
rack (1.5.2) lib/rack/session/abstract/id.rb:225:in `context'
rack (1.5.2) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/cookies.rb:486:in `call'
activerecord (4.0.0) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.0.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:626:in `call'
activerecord (4.0.0) lib/active_record/migration.rb:369:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.0.0) lib/active_support/callbacks.rb:373:in `_run__153816630__call__callbacks'
activesupport (4.0.0) lib/active_support/callbacks.rb:80:in `run_callbacks'
actionpack (4.0.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/reloader.rb:64:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/remote_ip.rb:76:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/debug_exceptions.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.0.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `block in call'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `block in tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:25:in `tagged'
activesupport (4.0.0) lib/active_support/tagged_logging.rb:67:in `tagged'
railties (4.0.0) lib/rails/rack/logger.rb:21:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.5.2) lib/rack/methodoverride.rb:21:in `call'
rack (1.5.2) lib/rack/runtime.rb:17:in `call'
activesupport (4.0.0) lib/active_support/cache/strategy/local_cache.rb:83:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
actionpack (4.0.0) lib/action_dispatch/middleware/static.rb:64:in `call'
railties (4.0.0) lib/rails/engine.rb:511:in `call'
railties (4.0.0) lib/rails/application.rb:97:in `call'
rack (1.5.2) lib/rack/lock.rb:17:in `call'
rack (1.5.2) lib/rack/content_length.rb:14:in `call'
rack (1.5.2) lib/rack/handler/webrick.rb:60:in `service'
C:/RailsInstaller/Ruby2.0.0/lib/ruby/2.0.0/webrick/httpserver.rb:138:in `service'
C:/RailsInstaller/Ruby2.0.0/lib/ruby/2.0.0/webrick/httpserver.rb:94:in `run'
C:/RailsInstaller/Ruby2.0.0/lib/ruby/2.0.0/webrick/server.rb:295:in `block in start_thread'

Answer 1

我想你要定义

resources :posts

而不是routes.rb文件中的单一资源。如果我没有弄错的话，redirect_to实际上是在尝试post_path(id)并不存在。

Answer 2

Sometimes it's helpful to me to look at somebody else's code like so many have posted on github. All the libraries for rails are on there anyway. Why not have a look. Maybe the tutorial code for the Michael Hartl book. https://github.com/mhartl/sample_app_3rd_edition Just things like that help me. There are many other full rails apps on github though besides this one. If you don't already have an account then you should get one to store your tutorial app on and we could just go look at it as if it were a code paste.

I believe this one is that Rails Guides blog app as far as I have gotten although I haven't worked with it for a while now. https://github.com/DouglasAllen/Rails-projects/blob/master/rails_docs/blog/config/routes.rb

That's the thing about Rails and some Ruby errors. You're (I'm) not always sure where it's coming from. Sometimes you just have to try different things. Don't give up. Save your code and go read some other articles. One that is official is fine but it's not the final word. Millions of other users are out there trying to make things work for them also. At least you have logging enabled don't you? I hope that is where you got your post for the error on here. If not, go find out how to use it. Then post it with your saved app.

Another great place to get some learning and some code is the Heroku Dev Center. Such as https://devcenter.heroku.com/articles/getting-started-with-rails4

Have fun!

Something you can play with but is a little insecure is environmental variables.

Try this in routes.rb

root 'application#env_vars'

and this in application_controller.rb

def env_vars
  vars = request.env.each
  render plain: "env #{vars.each {|v| v}}"
end

Almost as bad as chasing those stack traces.

If you have ever played around with Sinatra then you see that Rails routes are very similar because that's what Rack is for.

get '/vars' => 'application#env_vars'

is just an HTTP GET request. [URL]:[port]/map to controller-name#method or action as they call it. Resources include more than just the controller as models are involved as well. MVC is the Rails way. It lets you create all the parts at one time through the generators. But trains really use alternators these days. ;-)

学习本教程时的NoMethodError

2 个答案: