General rescue throughout controller when id not found - RoR

Question

I have stumbled upon a situation where my application looks for an id that does not exist in the database. An exception is thrown. Of course, this is a pretty standard situation

Answer 1

You must use rescue_from for this task. See example in the Action Controller Overview Guide

class ApplicationController < ActionController::Base
  rescue_from ActiveRecord::RecordNotFound, :with => :record_not_found

  private

  def record_not_found
    redirect_to action: :index
  end
end

Answer 2

Rails has a built-in rescue_from class method:

class CustomersController < ApplicationController
  rescue_from ActiveRecord::RecordNotFound, with: :index
  ...
end

Answer 3

In certain cases, I would recommend that you use Model.find_by_id(id) as opposed to Model.find(id). Instead of throwing an exception, .find_by_id returns nil. if the record could not be found.

Just make sure to check for nils to avoid NoMethodError!

P.S. For what it's worth, Model.find_by_id(id) is functionally equivalent to Model.where(id: id), which would allow you to build out some additional relations if you want.

Answer 4

If you're talking about doing this within a single controller (as opposed to doing this globally in every controller) then here are a couple options:

You can use a before_filter to setup your resource:

class CustomerController < ApplicationController
  before_filter :get_customer, :only => [ :show, :update, :delete ]

  def show
  end

  private

  def get_customer
    @customer = ActiveRecord.find(params[:id])
    rescue ActiveRecord::RecordNotFound
      redirect_to :action => :index
  end
end

Or you might use a method instead. I've been moving in this direction rather than using instance variables inside views, and it would also help you solve your problem:

class CustomerController < ApplicationController
  def show
    # Uses customer instead of @customer
  end

  private

  def customer
    @customer ||= Customer.find(params[:id])
    rescue ActiveRecord::RecordNotFound
      redirect_to :action => :index
  end
  helper_method :customer
end