Question

我使用has_many：通过collection_select在多选中通过多对多关系：multiple =＆gt;真正。我不明白，为什么“genre_ids”=＆gt; [“”，“2”，“3”，“4”]总是有空的第一个元素？

型号：

class Book < ApplicationRecord
  has_many :book_genres
  has_many :genres, through: :book_genres
end

class Genre < ApplicationRecord
  has_many :book_genres
  has_many :books, through: :book_genres
end

class BookGenre < ApplicationRecord
  belongs_to :book
  belongs_to :genre
end

_form.html.erb

<%= form_for @book do |f| %>
  ...
  <%= f.collection_select(:genre_ids, Genre.all, :id, :genre, {include_blank: "Select genre"}, {multiple: true, size: 6}) %>
  ...
  <%= f.submit %>
<% end %>

books_controller.rb

class BooksController < ApplicationController
  def new
    @book = Book.new
  end
  def create
    render plain: params.inspect
  end
end

参数：

<ActionController::Parameters {
  "utf8"=>"✓",
  "authenticity_token"=>"8WRSXJHwMyHM....",
  "book"=>{"title"=>"",
           "genre_ids"=>["", "2", "3", "4"],
           "desc"=>"",
           "published_at"=>"1982"}, 
  "commit"=>"Create Book", 
  "controller"=>"books",
  "action"=>"create"} permitted: false>

Answer 1

可能是因为“选择类型”也被选中，因为它是一个多选下拉列表。在将数据发送到服务器之前删除它，或者避免使用“include_blank”选项。

具有多个设置为true的Collection_select。为什么params [：book] [：genre_ids] = [“”，“1”，“2”]

1 个答案: