使用HABTM模型将外键自动从视图传递到控制器

Question

I have two models, Companies and Employees, with a many-to-many association between them.

class Company < ActiveRecord::Base
    has_and_belongs_to_many :employees
end

class Employee < ActiveRecord::Base
    has_and_belongs_to_many :companies
end

I have a join table :companies_employees

class CreateCompaniesEmployeesJoin < ActiveRecord::Migration
    def change
       create_table :companies_employees, :id => false do |t|
          t.integer "company_id"
          t.integer "employee_id"
       end
       add_index :companies_employees, ["company_id", "employee_id"]
    end
end

I have a Show view for Company, which includes a form_for adding a new Employee, who I want to associate with that Company via the HABTM association:

<%= form_for :employee, :url => employees_path do |f| %>
    <p>
        <%= f.label :name %>
        <%= f.text_field :name, class: 'form-control' %>
    </p>
    <br>
    <p>
        <%= f.hidden_field :company_id, :value => @company.id  %>
    </p>
    <p>
        <%= f.submit "Save Employee", class: "btn btn-default" %>
    </p>

<% end %> 

I have a controller for Employee, through which I want to create a new Employee that will be automatically associated with the Company from the Company Show view:

def create
    @company = Company.find(params[:company_id]) 
    @employee = Employee.new(employee_params)
    @company.employees << @employee

    if @employee.save
        flash[:success] = "Company Employee Added!"
        redirect_to @employee
    else
        render 'new'
    end
end

When I use the form to try to create a new employee, I get an error in EmployeeController -- "Couldn't find Company without an ID"

Seems my view is failing to pass the :company_id on to the create action in the EmployeeController.

I've scoured other posts and nothing seems to be on point. Any suggestions most appreciated!

Answer 1

Ok, the problem seems to be the nested attribute. Try to change in the EmployeesController#create the first row in:

@company = Company.find(params[:employee][:company_id])

EDIT

Alternatively, and probably more easy, you can also change the form hidden_field like this:

hidden_field_tag(:company_id, @company.id)