我有一个World父对象和一个State子对象。我正在尝试创建一个新的State对象，rails并没有找到世界ID。我正在尝试从世界展示页面链接到新状态表单，并且网址显示.../worlds/1/states/new，那么为什么这不会占用父ID？该错误应该来自控制器@world = World.find(params[:id])中的这一行。我尝试使用(params[:world_id])偶数。
为简洁起见，我只在这里发布相关代码。
world.rb
class World < ApplicationRecord
belongs_to :user
has_many :states
end
state.rb
class State < ApplicationRecord
belongs_to :world
belongs_to :user
end
states_controller.rb
class StatesController < ApplicationController
before_action :set_state, only: [:show, :edit, :update, :destroy]
before_action :authenticate_user!, except: [:index, :show]
def index
@states = State.all
end
def new
@world = World.find(params[:id])
@state = @world.states.build
end
def create
@world = World.find(params[:id])
@state = @world.states.build(state_params)
@state.user = current_user
respond_to do |format|
if @state.save
format.html { redirect_to @state, notice: 'State was successfully created.' }
else
format.html { render :new }
end
end
end
private
def set_state
@state = State.find(params[:id])
end
def state_params
params.require(:state).permit(:name, :summary, :history, :population, :inception, :life_expectancy, :land_mass,
:climate, :industry, :education, :mythology, :law, :culture, :world_id, :user_id)
end
end
worlds / show.html.erb中新状态表单的链接：
<%= link_to 'New State', new_world_state_path(@world) %>
的routes.rb
Rails.application.routes.draw do
resources :states
resources :worlds
devise_for :users, path: '', path_names: { sign_in: 'login', sign_out: 'logout', sign_up: 'register' }
root to: "home#index"
resources :users
resources :worlds do
resources :states
end
end
的状态/ _form.html.erb
<div class="form">
<%= form_for(state) do |f| %>
<% if state.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(world.errors.count, "error") %> prohibited this state from being saved:</h2>
<ul>
<% state.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<%= f.text_field :name, placeholder: 'Name' %><br />
<fieldset>
<legend>Basic Info</legend>
<%= f.text_area :summary, placeholder: 'Summary About', rows: 6 %><br />
<%= f.text_area :history, placeholder: 'History', rows: 6 %><br />
<%= f.text_area :climate, placeholder: 'Climate', rows: 3 %><br />
<%= f.text_area :industry, placeholder: 'Industry', rows: 3 %><br />
<%= f.text_area :education, placeholder: 'Education', rows: 3 %><br />
<%= f.text_area :culture, placeholder: 'Culture', rows: 3 %><br />
<%= f.text_area :law, placeholder: 'Legal System, Crime & Punishment', rows: 3 %><br />
<%= f.text_area :mythology, placeholder: 'Mythology', rows: 3 %><br />
</fieldset>
<fieldset>
<legend>Quick Stats</legend>
<%= f.text_field :inception, placeholder: 'Inception' %><br />
<%= f.text_field :population, placeholder: 'Population' %><br />
<%= f.text_field :life_expectancy, placeholder: 'Ave. Life Expectance' %><br />
<%= f.text_field :land_mass, placeholder: 'Land Mass' %><br />
</fieldset>
<p><%= f.submit %></p>
<% end %>
</div>
导出控制台结果
Started GET "/worlds/1/states/new" for 70.196.17.76 at 2017-05-22 13:43:47 +0000
Cannot render console from 70.196.17.76! Allowed networks: 127.0.0.1, ::1, 127.0.0.0/127.255.255.255
Processing by StatesController#new as HTML
Parameters: {"world_id"=>"1"}
User Load (0.3ms) SELECT "users".* FROM "users" WHERE "users"."id" = ? ORDER BY "users"."id" ASC LIMIT ? [["id", 2], ["LIMIT", 1]]
World Load (0.1ms) SELECT "worlds".* FROM "worlds" WHERE "worlds"."id" = ? LIMIT ? [["id", nil], ["LIMIT", 1]]
Completed 404 Not Found in 3ms (ActiveRecord: 0.4ms)
ActiveRecord::RecordNotFound (Couldn't find World with 'id'=):
app/controllers/states_controller.rb:13:in `new'
Rendering /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout
Rendering /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/_source.html.erb
Rendered /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/_source.html.erb (4.7ms)
Rendering /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb
Rendered /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.6ms)
Rendering /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb
Rendered /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (1.1ms)
Rendered /usr/local/rvm/gems/ruby-2.3.0/gems/actionpack-5.0.3/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (36.6ms)
答案 0 :(得分：2)
修改您的link_to帮助程序，以指定并告诉Rails您通过它发送的参数：
自：
<%= link_to 'New State', new_world_state_path(@world) %>
要：
<%= link_to 'New State', new_world_state_path(id: @world) %>
id，因为您试图通过World作为参数找到:id。
还尝试更改在您设置param变量的控制器中收到的@world：
def new
@world = World.find(params[:world_id])
...
end
在show.html.erb：
<%= link_to 'New World', new_world_state_path(world_id: @world) %>
更新：我们做了什么：
在app/views/worlds/show.html.erb中更改参数的设置方式：
自：
<%= link_to 'New Nation', new_world_state_path(world_id: @world_id) %> # @world_id wasn't defined
要：
<%= link_to 'New Nation', new_world_state_path(world_id: @world.id) %>
在/app/views/states/_form.html.erb中将world_id添加为hidden_field：
<%= f.hidden_field :world_id, value: @world.id %>
然后在app/controllers/states_controller.rb改变接受参数的方式：
def new
@world = World.find(params[:world_id])
@state = @world.states.build
end
def create
@world = World.find(params[:state][:world_id])
...
答案 1 :(得分：2)
当world_id传递给：new操作时，它可能不会在表单上传回给创建操作。
你的state_params期待a：world_id被发送回来，所以添加一个隐藏字段将其发送回表格。
new.html.erb
<%= f.hidden_field :world_id, :value => @world.id %>
并将创建操作更新为
@world = World.find(params[:world_id])