Rails 4 use params from controller in a callback (model) function

Question

Rails 4, Ruby 2.3.1 (noob alert)

I have a restaurant reservation app. before a reservation is saved I need to check the db to ensure there is a table available. To do this I check the date and time selected in the form with a count:

Reservation.where(r_date:params[:r_date],r_time:params[:r_time]).count < 3

assuming the restaurant has 3 tables. If the count is more than 3 then there is not a table available.

How do I get the params from @reservation in the controller to the callback function in the model?

Where is @reservation var in your controller and what is "callback function in the model"? It is not quite clear what you mean. — Uzbekjon
– Uzbekjon, Commented Jun 23, 2016 at 4:34

Austin Pocus · Accepted Answer · 2016-06-23 04:35:48Z

1

You can use a before_save method to check availability, and invalidate the model, canceling the save, if there are no tables available.

In your controller:

class ReservationsController < ApplicationController
  def create
    @reservation = Reservation.new(reservation_params)
    if @reservation.save
      redirect_to reservation_path(@reservation)
    else
      render 'new'
    end
  end

  private

  def reservation_params
    params[:reservation].permit(:r_date, :r_time)
  end
end

Then, in your model:

class Reservation < ActiveRecord::Model
  before_save :check_availability

  private

  def check_availability
    reservation_count = Reservation.where(r_date: self.r_date, r_time: self.r_time).count
    if reservation_count > 3
      return false
    end
  end
end

I haven't had a chance to test this code, so please let me know if you have any problems.

Edit: explanation

answered Jun 23, 2016 at 4:35

Austin Pocus

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2 Comments

phillipjones1 Over a year ago

thank you ajpocus! How do I add a flash or error to this callback?

Austin Pocus Over a year ago

No problem @phillipjones1! You should be able to set flash[:notice] = "your message here" before the render 'new' call.

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