Validate unique array values in Rails

Question

My Transaction model generates an array of unique ticket numbers based on quantity (an integer column) with the following controller logic:

@transaction.quantity.times.uniq { @transaction.ticket_numbers << rand(100000..999999) }

However, this only ensures that the numbers WITHIN the array are unique.

I need a database validation that checks ALL Transaction.ticket_numbers arrays to ensure that every value (ticket number) is unique across ALL arrays.

Here is my Transaction table within schema.rb:

  create_table "transactions", force: :cascade do |t|
    t.string "payee"
    t.integer "quantity"
    t.decimal "debt", precision: 8, scale: 2
    t.string "email"
    t.string "ministry"
    t.integer "status"
    t.integer "user_id"
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.integer "ticket_numbers", default: [], array: true
  end

Transaction model from transaction.rb:

require 'csv'

class Transaction < ApplicationRecord
  belongs_to :user

  validates :email, :format => { :with => /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/, :on => [:create, :update] }
  validates :payee, presence: true
  validates :quantity, numericality: { greater_than_or_equal_to: 1 }
  validates :debt, numericality: { greater_than_or_equal_to: 0 }

  def self.to_csv
    attributes = %w{payee email ministry quantity debt status ticket_numbers}
    CSV.generate(headers: true) do |csv|
      csv << attributes
      all.each do |transaction|
        csv << attributes.map{ |attr| transaction.send(attr) }
      end
    end
  end
end

Transaction controller:

class TransactionsController < ApplicationController
  before_action :load_transaction, only: [:edit, :update, :destroy]

  def create
    @transaction = Transaction.new(transaction_params)
    if @transaction.save
      @transaction.quantity.times.uniq { @transaction.ticket_numbers << rand(100000..999999) }
    end
    @user = @transaction.user
    @transactions = @user.transactions
    respond_to do |format|
      if @transaction.save && @transaction.status == 1
        UserMailer.payment_confirmation(@transaction).deliver_later
        format.html { redirect_to user_url(@user), notice:'Transaction added & ticket sent' }
        format.json { render json: @user, status: :created, location: @user }
      elsif @transaction.save && @transaction.status != 1
        format.html { redirect_to user_url(@user), notice:'Transaction added' }
        format.json { render json: @user, status: :created, location: @user }
      else
        format.html { render 'users/show' }
        format.json { render json: @transaction.errors, status: :unprocessable_entity }
      end
    end
  end

  def edit
    @user = current_user
  end

  def update
    update_ticket_numbers
    respond_to do |format|
      if @transaction.update_attributes(transaction_params) && @transaction.status == 1
        UserMailer.payment_confirmation(@transaction).deliver_later
        format.html { redirect_to user_url(current_user), notice: 'Transaction info updated & confirmation email sent to payee' }
        format.json { render json: current_user, status: :created, location: current_user }
      elsif @transaction.update_attributes(transaction_params) && @transaction.status != 1
        format.html { redirect_to user_url(current_user), notice: 'Transaction info updated' }
        format.json { render json: current_user, status: :created, location: current_user }
      else
        format.html { render :edit }
        format.json { render json: @transaction.errors, status: :unprocessable_entity }
      end
    end
  end

  def destroy
    @transaction.destroy
    redirect_to user_url(current_user), notice: 'Transaction deleted'
  end

  private

  def load_transaction
    @transaction = Transaction.find(params[:id])
  end

  def transaction_params
    params.require(:transaction).permit(:payee, :email, :ministry, :debt,
    :quantity, :status, :user_id, :ticket_numbers)
  end

  def update_ticket_numbers
    if @transaction.update_attributes(transaction_params)
      if @transaction.ticket_numbers.length < @transaction.quantity
        i = @transaction.quantity - @transaction.ticket_numbers.length
        i.times.uniq { @transaction.ticket_numbers << rand(100000..999999) }
      elsif @transaction.ticket_numbers.length > @transaction.quantity
        i = @transaction.ticket_numbers.length - @transaction.quantity
        i.times { @transaction.ticket_numbers.pop }
      end
    end
  end

end

Would it be easier to work with ticket numbers if they were in their own separate model/table instead of an array? — Brad Werth
– Brad Werth, Commented Aug 16, 2017 at 20:03
I can see what you're getting at, but if I use a separate model it would be purely for generating ticket numbers which can be added & removed when Transaction.quantity is edited. I also use ActionMailer to automate emails when transactions are marked complete on the form. Wouldn't a ticket number model be excessive for this? Thanks! — D Cheeles
– D Cheeles, Commented Aug 16, 2017 at 21:12
I'm no expert but can't you try intersections of all the arrays and check if the intersection is empty to find uniqueness? — Jeeppp
– Jeeppp, Commented Aug 16, 2017 at 21:19
@D_Cheeles I think Brad's suggestion will ultimately be less excessive than the path you are currently on. Databases are good at unique constraints. You should take advantage of that if you can. — Wizard of Ogz
– Wizard of Ogz, Commented Aug 17, 2017 at 0:25
@DCheeles, there's a joke that goes "Boss, I wrote a program that does the wrong thing but does it really fast". Make it right first, worry about performance later when it becomes an issue. Like other have said, I think you should create a separate model for the Ticket and implement the constraint with a unique index. — Greg Navis
– Greg Navis, Commented Aug 17, 2017 at 4:57

Clue · Accepted Answer · 2020-08-19 22:43:20Z

1

You can add a custom ticket number validation to your model. You can read more about them here

class Transaction < ApplicationRecord
  validate :ticket_number_uniqueness

  def ticket_number_uniqueness
    # First check all new ticket numbers are unique from each other
    errors.add(:ticket_number, "is not unique") unless ticket_numbers == ticket_numbers.uniq
    
    # Next check against other ticket numbers
    ticket_numbers.each do |ticket|
      if ::Transaction.where("ticket_numbers @> '{?}'", ticket).exists?
        errors.add(:ticket_number, "is not unique")
      end
    end
  end
end

Note: this is taking advantage of Postgres contains array method @>. You can learn more about array methods here

answered Aug 19, 2020 at 22:43

Clue

111 bronze badge

Sign up to request clarification or add additional context in comments.

5 Comments

Kaom Te Over a year ago

This looks like this should work without a separate Ticket model. One thing I would change is the ticket_numbers == ticket_numbers.uniq comparison. There is no guarantee that the order will be consistent against the original after the call to uniq. Sorting should be applied or alternatively a set comparison should be made instead.

Clue Over a year ago

What makes you think the order isn't guaranteed? apidock.com/ruby/Array/uniq. I would suggest a simple length comparison ticket_numbers.size == ticket_numbers.uniq.size as an alternative, which may give a performance improvement as well, but wanted to keep things simple in my answer.

Kaom Te Over a year ago

Strictly speaking, the order is not guaranteed. The documentation there says nothing about the order of the returned array. Practically speaking, you're probably right though.

svelandiag Over a year ago

why do you use double colon operator before Transaction model?

Clue Over a year ago

Habit ¯_(ツ)_/¯. It's not necessary, but it is explicit.

Collectives™ on Stack Overflow

Validate unique array values in Rails

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related