Rails表单提交值为nil无法插入，且show动作缺失引发报错

问题现象 #

1. 提交表单创建God记录时，数据库插入的name、ph_no、bhakts字段均为nil，而非表单填写的值
2. 记录创建成功后重定向到show页面，因GodsController未定义show动作，触发AbstractController::ActionNotFound错误

相关代码与日志 #

GodsController #

class GodsController < ApplicationController
    def index
        @g=God.all
    end
    def new
        @g=God.new()
    end
    def create
        @g=God.new(g_params)
        if @g.save
            redirect_to @g
        else
            render :new, status: :unprocessable_entity
        end
    end
    def g_params
        params.fetch(:g,{}).permit(:name , :ph_no , :bhakts)
    end
end

schema.rb #

ActiveRecord::Schema[7.0].define(version: 2023_04_18_112327) do
  create_table "gods", force: :cascade do |t|
    t.string "name"
    t.string "ph_no"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "bhakts"
  end
end

God模型 #

class God < ApplicationRecord
end

新建表单视图（new.html.erb） #

<h1> Insert new God </h1>

<%= form_with model: @g do |form| %>
<div>
<%= form.label :name %>
<%= form.text_field :name %>
</div>
<div>
<%= form.label :ph_no %>
<%= form.text_field :ph_no %>
</div>
<div>
<%= form.label :bhakts %>
<%= form.text_field :bhakts %>
</div>
<div>
<%= form.submit%>
</div>
<%end %>

列表视图（index.html.erb） #

<h1> <b> MY GODS !! </b></h1>

<table>
<thead>
<tr>
<th> Name</th>
<th> ph_no</th>
<th> Bhakts</th>
</tr>
</thead>
<tbody>
 <% @g.each do |x| %>
 <tr>
 <td><%= x.name%></td>
 <td><%= x.ph_no%></td>
<td><%= x.bhakts%></td>
</tr>
<% end%>
</tbody>
</table>

终端日志 #

Started POST "/gods" for ::1 at 2023-04-20 12:29:09 +0530
Processing by GodsController#create as TURBO_STREAM
  Parameters: {"authenticity_token"=>"[FILTERED]", "god"=>{"name"=>"Divya Pratap Singh", "ph_no"=>"76678", "bhakts"=>"45"}, "commit"=>"Create God"}
  TRANSACTION (0.2ms)  begin transaction
  ↳ app/controllers/gods_controller.rb:10:in `create'
  God Create (1.0ms)  INSERT INTO "gods" ("name", "ph_no", "created_at", "updated_at", "bhakts") VALUES (?, ?, ?, ?, ?)  [["name", nil], ["ph_no", nil], ["created_at", "2023-04-20 06:59:09.914114"], ["updated_at", "2023-04-20 06:59:09.914114"], ["bhakts", nil]]
  ↳ app/controllers/gods_controller.rb:10:in `create'
  TRANSACTION (0.7ms)  commit transaction
  ↳ app/controllers/gods_controller.rb:10:in `create'
Redirected to http://localhost:3000/gods/15
Completed 302 Found in 10ms (ActiveRecord: 1.9ms | Allocations: 2305)


Started GET "/gods/15" for ::1 at 2023-04-20 12:29:09 +0530
  
AbstractController::ActionNotFound (The action 'show' could not be found for GodsController):
  
 `block in spawn_thread'
Started GET "/gods/new" for ::1 at 2023-04-20 12:29:10 +0530
Processing by GodsController#new as HTML
  Rendering layout layouts/application.html.erb
  Rendering gods/new.html.erb within layouts/application
  Rendered gods/new.html.erb within layouts/application (Duration: 1.1ms | Allocations: 1174)
  Rendered layout layouts/application.html.erb (Duration: 2.7ms | Allocations: 3313)
Completed 200 OK in 3ms (Views: 3.0ms | ActiveRecord: 0.0ms | Allocations: 3585)

解决办法 #

1. 修复参数获取错误 #

从终端日志可见，表单提交的参数键是god，但控制器的g_params方法里误用了:g，导致无法正确读取表单值，最终所有字段插入为nil。修改g_params方法：

def g_params
  params.fetch(:god, {}).permit(:name, :ph_no, :bhakts)
end

2. 解决show动作缺失问题 #

有两种方案可选：

方案一：添加show动作及对应视图

在GodsController中新增show动作：

def show
  @g = God.find(params[:id])
end

然后创建app/views/gods/show.html.erb视图文件，示例内容：

<h1><%= @g.name %></h1>
<p>手机号: <%= @g.ph_no %></p>
<p>信徒数量: <%= @g.bhakts %></p>
<%= link_to '返回列表', gods_path %>

方案二：修改重定向目标到列表页

如果不需要单独的详情页面，可修改create动作的重定向逻辑，跳转到列表页：

def create
  @g=God.new(g_params)
  if @g.save
    redirect_to gods_path, notice: '记录创建成功'
  else
    render :new, status: :unprocessable_entity
  end
end

内容的提问来源于stack exchange，提问作者BrownboyD