[Rails] Why is id off by one or defined different in edit vs in update?

Ruby on Rails Friday, June 8, 2018

why is id off by one or defined different in edit vs in update? I will explain what I mean

I have a controller called Bottles and a model Bottle

My config\routes.rb file has the line- resources :bottles

I have this controller

class BottlesController < ApplicationController
  def index
  end

  def show
  end

  def edit
    # http://127.0.0.1:3000/bottles/0/edit       :id==0
    
    # <ActionController::Parameters {"controller"=>"bottles", "action"=>"edit", "id"=>"0"} permitted: false>
    
# Bottle.all[0] gives <Bottle id: 1, name: "tod", size: 234,...>
   
    @bottle=Bottle.all[params[:id].to_i]   #:id==0
  end


I have these views

C:\rubytest\testoby>type app\views\bottles\new.html.erb
<%= form_for @bottle do |f| %>
<%= f.text_field :name %>
<%= f.text_field :size %>
<%= f.submit "Create" %>
<% end %>

C:\rubytest\testoby>type app\views\bottles\edit.html.erb
<%= form_for @bottle do |f| %>
<%= f.text_field :name %>
<%= f.text_field :size %>
<%= f.submit "Save" %>
<% end %>
C:\rubytest\testoby>

I went to http://127.0.0.1:3000/bottles/new and I made a bottle

name- tod
size- 234


I then go to http://127.0.0.1:3000/bottles/0/edit

and I see the bottle there in the form

I then change tod to todd and click 'save'


here's the weird thing


I see the URL change to

http://127.0.0.1:3000/bottles/1


but i'd expect it to change to

http://127.0.0.1:3000/bottles/0


I'd expect the form to be submitted to /bottles/0 but it's not, it's submitted to /bottles/1


And the params have :id=1


So when it comes to my update, I have to write this line in the controller, subtracting 1 from the id


@abottle=Bottle.all[params[:id].to_i-1]


I can see that there is a difference of definition of :id that one could use… The id in the URL could be either 

A)The index in the array e.g. Bottle.all[params[:id]] (Which is what i've got for the edit action). or 

B) The id attribute of the object, (Which is what i've got for the update action @abottle=Bottle.all[params[:id].to_i-1]


One could say, it's 'A', the URL. But then why should the update URL have an :id that is one up from the ID in the edit URL?


Thanks

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Posted by Ruby on Rails at 12:54 PM

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