[RUBY] [Rails] How to register multiple records in the intermediate table with many-to-many association

Features you want to implement

In a many-to-many model relationship, I want to register multiple selected values in the intermediate table with the check box. I was really into it when I implemented it, so I'll leave it as a memorandum.


Rails 5.2 Ruby 2.5.1 MacOSX

Model relationship

--Project model

class Project < ApplicationRecord
  has_many :project_phases, dependent: :destroy
  has_many :mst_phases, through: :project_phases

--Project process

class ProjectPhase < ApplicationRecord
  belongs_to :project
  belongs_to :mst_phase

--Process master

class MstPhase < ApplicationRecord
  has_many :project_phases

Regarding the process, only the project_phase model is associated in the master table so that the project model side is not referenced.


<%= form_with model: @project, local: true do |f| %>
  <label>Project name</label>
  <%= f.text_field :project_name %>

  <label>Project process</label>
  <%= f.collection_check_boxes :mst_phase_ids, MstPhase.all, :id, :phase %>
<% end %>


class ProjectsController < ApplicationController

  def new
    @project = Project.new

  def create
    @project = Project.new(projects_params)
    if @project.save
      redirect_to project_path @project
      render action: 'new'

  def projects_params
    params.require(:project).permit( :project_name, mst_phase_ids: [])

The point is to set StrongParameter to receive models related to has_many as an array.

The names of the parameters should be described as follows.

Model name_ids

Since it is not necessary to implement any special logic for the parameters received in the array, records are registered in the table for the number of elements in the array. Rails convenient. .. .. .. ..

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