Adding an object to one to many relationship ROR - ruby-on-rails

Question

I am having trouble adding an object to associate class.
the parent class, user, has a has_many relation with the ad class.
When i try to access user's has_many object ":ads" from the ad controller, it returns me an "undefined method ads" exception. I am posting my model and my controller code below. Please help me on this issue.
user model
class User < ActiveRecord::Base
has_many :ads
has_secure_password
has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "50x50#" }, :default_url => "/images/:style/missing.png"
validates_attachment_content_type :avatar, :content_type => /\Aimage\/.*\Z/
def self.searchID(query)
where("id like ?", "#{query}")
end
end
ad model
class Ad < ActiveRecord::Base
belongs_to :user
scope :orderNewestFirst , lambda { order("id DESC") }
has_attached_file :avatar, :styles => { :medium => "300x300>", :thumb => "100x100#" }, :default_url => "/images/:style/missing.png"
validates_attachment_content_type :avatar, :content_type => /\Aimage\/.*\Z/
def self.search(query)
where("title like ?", "%#{query}%")
end
end
Ad Controller
class AdController < ApplicationController
layout false
before_action :confirm_logged_in
def index
#ads = Ad.orderNewestFirst
end
def new
#ad = Ad.new()
end
def create
#find = session[:user_id]
#user = User.searchID(#find)
#ad = Ad.new(ad_params)
if #user.ads << #ad #***this is where the error is occuring***
flash[:notice] = "Ad created Successfully"
redirect_to(:controller => 'user' , :action => 'index')
else
render('new')
end
end
def show
#ad = Ad.find(params[:id])
end
def ad_params
params.require(:ad).permit(:title, :category, :description , :priceRange, :avatar )
end
end
EDIT
Here are my migrations for User and Ad
User Migration
class CreateUsers < ActiveRecord::Migration
def up
create_table :users do |t|
t.string "firstName" , :limit => 50 , :null => false
t.string "lastName" , :limit => 50
t.string "email" , :null => false
t.string "password" , :limit => 30 , :null => false
t.integer "rating" , :default => 0
t.string "location" , :default => "Lahore"
t.timestamps null: false
end
end
def down
drop_table :users
end
end
#user = User.new(:firstName => "" , :lastName => "" , :email => "" , :password => "" , :rating => "" , :location => "")
Ad Migration
class CreateAds < ActiveRecord::Migration
def up
create_table :ads do |t|
t.references :user
t.string "title" , :null => false
t.string "category" , :null => false
t.text "description"
t.string "priceRange" , :null => false
t.attachment :avatar
t.timestamps null: false
end
add_index("ads" , "user_id")
end
def down
drop_table :ads
end
end
#ad = Ad.new(:title => "" , :category => "" , :description => "" , :priceRange => "")
The error that i get..

Answer 1

Your User.searchID(query) returns multiple user records (a relation object), not a single one.
If you change it to User.searchID(query).take, it fetches only a single record, and the error vanishes.
I don't know what value session[:user_id] holds, but looking at your users table, this would simply be an integer ID? In that case, there isn't much sense in the current approach. I'd recommend something like this:
def create
#user = User.find(session[:user_id])
# Rest of create method
end
The User.find method looks for a user record with that exact ID, and will return a single record straight away. This is one of the most common ways to fetch records using Ruby on Rails.

Answer 2

I am not sure how like query with id is working for you, In postgres it doesn't
def self.searchID(query)
where("id like ?", "#{query}")
end
You don't need above method you can find user directly by id as
#user = User.find(session[:user_id])