Question

我只是学习RoR，现在混淆了如何将数据插入db。这是我的代码：

book_insert.html.erb

<%= content_for :helloworld do %>
    <%= form_tag("/insert", method: "post") do %>
        <%= label_tag(:title, "Title") %>
        <%= text_field_tag(:title) %><br>
        <%= label_tag(:price, "Price") %>
        <%= number_field_tag(:price) %><br>
        <%= label_tag(:subject_id, "Subject ID") %>
        <%= number_field_tag(:subject_id) %><br>
        <%= label_tag(:description, "Description") %>
        <%= text_field_tag(:description) %><br>
        <br>
        <%= submit_tag("Submit") %> 
    <% end %>
<% end %>

book_controller.rb

class BookController < ApplicationController
    def insert
        @book = Book.new(book_params)
        @book.save
        render :book_page
    end

    def book_params
        params.require(:books).permit(:title, :price, :subject_id, :description)
    end

    def showinsert
        render :book_insert
    end
end

它返回错误：

在4毫秒内完成了400错误请求（ActiveRecord：0.0毫秒） ActionController :: ParameterMissing（缺少参数或值为空：书籍）：

请帮助。谢谢

Answer 1

form_tag通常用于向映射的controller#action提交非模型动作。您可能需要在表单内使用form_for及其相应的助手

<%= content_for :helloworld do %>
  <%= form_for Book.new, url: "/insert", method: "post" do |f| %>
    <%= f.label :title %>
    <%= f.text_field :title %><br>
    <%= f.label :price %>
    <%= f.number_field :price %><br>
    <%= f.label :subject_id %>
    <%= f.number_field :subject_id %><br>
    <%= f.label :description %>
    <%= f.text_field :description %><br>
    <br>
    <%= f.submit "Submit" %> 
  <% end %>
<% end %>

使用上面的代码，params将传递到:book => {}哈希中，因此您需要将book_params更改为下面的

def book_params
  params.require(:book).permit(:title, :price, :subject_id, :description)
end              #^

Answer 2

params.require方法要求密钥books存在于哈希中-如果不存在，则会引发ActionController::ParameterMissing异常。

要嵌套输入，您需要相应地命名它们：

<%= form_tag("/insert", method: "post") do %>
  <%= label_tag("Title") %>
  <%= text_field_tag("books[title]") %><br>
  <%= label_tag("Price") %>
  <%= number_field_tag("books[price]") %
  ...
  <%= submit_tag("Submit") %> 
<% end %>

这将使参数散列：

{ books: { title: 'Life & Times of Michael K', price: 99 } }

但是那很乏味。更好的方法是使用表单助手，并按照约定设置路由和控制器：

# config/routes.rb
resources :books

# app/views/books/new.html.erb
<%= form_for(@book) do |f| %>
  <div class="field">
    <%= f.label :title %>
    <%= f.text_field :title %>
  </div>
  # ...
  <%= f.submit %>
<% end %>

# app/controllers/books_controller.rb
class BooksController < ApplicationController
  # this renders the form to create a new book
  # GET /books/new
  def new
    @book = Book.new
  end

  # In Rails its called create - not insert
  # POST /books
  def create
    @book = Book.new(book_params)
    if @book.save
      redirect_to @book
    else
      render :new
    end
  end

  # This is the path to show a book
  # its also where we redirect after creating the book
  # GET /books/:id
  def show
    @book = Book.find(params[:id])
  end

  # ...

  private 
    def book_params
      # note thats its book singular - not plural
      params.require(:book).permit(:title, :price, :subject_id, :description)
    end
end

Answer 3

您应该在book方法中执行book_params，而不是books：

def book_params
    params.require(:book).permit(:title, :price, :subject_id, :description)
end

无法将数据插入Rails中的Ruby中的数据库

3 个答案: