How to pass parameters when building an Object in Rails controller

Question

I have an Event model and a Notifications model. An event has many notifications, and a notification only has one event. My notification object has two attributes: message and event_id. When I build a new notification, how can I set the event_id to the current event's id?

events_controller.rb

class EventsController < ApplicationController

before_action :signed_in, only: [:new,:create]

def new
    @event = Event.new
end

def create
    @event = Event.new(event_params)
    if @event.save
        flash[:success] = "Your Event has been created."
        redirect_to root_path
    else
        render 'new'
    end
end

def show
    @event = Event.find(params[:id])
    @notification = @event.notifications.build
    respond_to do |format|
      format.html
      format.xml  { render :xml => @event }
      format.json { render :json => @event }
    end
end

private

    def event_params
        params.require(:event).permit(:name, :description)
    end

    def signed_in
        unless user_signed_in?
            redirect_to new_user_session_path
            flash[:warning] = "You must be signed in to access that page"
        end
    end
end

notifications_controller.rb

class NotificationsController < ApplicationController

def create
    @notification = Notification.new(notification_params)
    if @notification.save
        redirect_to root_path
        flash[:success] = "Your message has been sent"
    else
        render 'new'
    end
end

def show
end

private

    def notification_params
        params.require(:notification).permit(:message, :event_id)
    end

    def signed_in
        unless user_signed_in?
            redirect_to new_user_session_path
            flash[:warning] = "You must be signed in to access that page"
        end
    end
end

routes.rb

devise_for :users
resources :events
resources :notifications
root 'static_pages#home'
match '/help',    to: 'static_pages#help',    via: 'get'
match '/about',   to: 'static_pages#about',   via: 'get'
match '/contact', to: 'static_pages#contact', via: 'get'

Answer 1

@notification = @event.build_notification(notification_params)