Nested Simple Form in Rails4 - has many through, save multiple records

问题

I've got a standard has_many through relationship. Humans have many Orcs through a join table Interactions. The interactions is just a table and model; no controller or views.

Using the simpleform gem in Rails 4, I want to make a form from the humans page, in order to select multiple orcs out of the pool of all orcs. Once submitted, I want it to create/update as many records in the interactions table, each with the human id, and as many orc ids were selected. :

AKA list notation

Make a form from one end (humans)
List out all the orcs in the form
Select multiple orcs from that list
Save as many records into the interactions table with human_id and orc_id as there were orcs chosen from that list. (The human_id will be the same in these records, since it started from a given human's form page)

I'll code out as much of the entire story as I have. Please feel free to ask for clarifications, and fix anything wrong for accomplishing this.

Tables

humans
  integer "id"

interactions
  integer "human_id"
  integer "orc_id"


  index ["human_id", "orc_id"] 
  # This is the primary key. no normal id.
  # Is it better to have a primary id for this join table, or does it not matter?

orcs
  integer "id"

Models

/models/human.rb

class Human < ActiveRecord::Base
  has_many :interaction
  has_many :orcs, through: :interactions

  accepts_nested_attributes_for :interactions
end

/models/interaction.rb

# Purely a join model and table. No controller, no scaffold.
class Interaction <ActiveRecord::Base
  belongs_to :human
  belongs_to :orc

  accepts_nested_attributes_for :orc 
  # Singular to match what was specified in the belongs_to relationship?
  # Do I even need this if I'm only trying to read orcs to save their id into the interactions table, and not trying to modify orcs?
end

/models/orc.rb

class Orc< ActiveRecord::Base
  has_many :interactions
  has_many :humans, through: :interactions

end

Controllers

/controllers/humans_controller.rb

class HumansController < ApplicationController

  before_action :set_human,         only: [:show, :edit, :update, :destroy]
  before_action :build_interaction, only: [:new, :edit]

  private
    def set_human
      @human = Human.find(params[:id])
    end

    def human_params
      params.require(:human).permit(
                                    interaction_attributes: [:human_id, 
                                                             :orc_ids,   # Is plural here correct?
                                                             :_destroy]
      )
    end

    def build_interaction
      @interaction = @human.interactions.build
                     # Is the human instance variable valid here?
                     # How many interactions are being built here?
                     # How do I ensure there are as many interaction builds as there will be selected orcs (i.e. as many interaction records to be saved or updated)?
    end
end

/controllers/orcs_controller.rb

class OrcsController < ApplicationController

  before_action :set_orc,   only: [:show, :edit, :update, :destroy]

  private
    def set_orc
      @orc = Orc.find(params[:id])
    end

    def orc_params
      params.require(:orc).permit()
    end

end

Views

/views/humans/_form.html.haml

= simple_form_for(@human, html: { multipart: true }) do |f|
  = f.simple_fields_for :interactions do |i|
    = i.hidden_field :human_id, value: @human.id
    = i.association :orc, collection: Orc.all
                    ^                        
                    # Should this be :orc_id?
                    # Does this code automatically extract the orc_id when saving to the interactions table?

Thank you.

What am I missing? when I submit, I confirmed that there no record created in the interactions join table.

I think some of the challenges are

creating multiple records reusing the single hidden input field.
obtaining a list of orcs when the interactions table must be a singular orc (since it was defined with belongs_to :orc in the interactions model)

Also, where can I find out more about how using the plural form of model ids works (i.e. simply using orc_ids instead of orc_id, and what concrete consequences that entails)?

回答1:

Turns out that with simple_form this is actually rather simple (who knew?). It handles the magic of all the intermediary tables (together with Rails's awesomeness). All you need to do is this:

= simple_form_for(@human, html: { Pmultipart: true }), do |f|
  = f.association :orcs

I don't really use HAML so I'm not sure about that comma before do |f|. Here is what I'm trying to say in ERB HTML

<%= simple_form_for(@human) do |f| %>
  <%= f.association :orcs %>
<% end %>

Then in your controller's param sanitizer:

def orc_params
  params.require(:orc).permit(orc_ids: [])
end

And finally in your model:

class Human < ActiveRecord::Base
  ...
  accepts_nested_attributes_for :orcs
end

And that's it! It will automatically create the join objects. Don't you just love magic?

This will generate a multi-select field populated by all orcs. You can easily change this to checkboxes by using f.association :orcs, as: :check_boxes.

来源：https://stackoverflow.com/questions/25101933/nested-simple-form-in-rails4-has-many-through-save-multiple-records

标签

ruby-on-rails

simple-form

nested-forms

has-many-through