Yaay! I'm happy to report success with my first attempt to make a Rails
app that works from an existing database.
This first experiment used (a) the simplest "instructions" I could find
(basically, Hassan's); (b) a streamlined version of the "Getting Started
Guide" process for setting up a Rails app (but - this is crucial -
*omitting* the step of running the migrator); and (c) a pre-existing
("legacy") database that conforms to the Rails naming conventions.
For the benefit of other Rails newbies (or oldbies) that need to build apps
on existing DBs, a play-by-play of what I did follows.
1. Created new Rails app, *x*:
[sunward@web324 rails_eval]$ rails new x
2. Populated the "legacy" SQLite database with table toys, and added one
row to that table:
[sunward@web324 x]$ rails dbconsole
SQLite version 3.6.20
sqlite> CREATE TABLE toys ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
"name" TEXT);
sqlite> INSERT INTO toys (name) VALUES ("Tinker");
sqlite> SELECT * FROM toys;
1|Tinker|58
3. Added the *toys *resource and root to *routes.rb*:
Rails.application.routes.draw do
resources :toys
root 'toys#index'
end
4. Used *rake *to see the resulting routes:
[sunward@web324 x]$ rake routes
Prefix Verb URI Pattern Controller#Action
toys GET /toys(.:format) toys#index
POST /toys(.:format) toys#create
new_toy GET /toys/new(.:format) toys#new
edit_toy GET /toys/:id/edit(.:format) toys#edit
toy GET /toys/:id(.:format) toys#show
PATCH /toys/:id(.:format) toys#update
PUT /toys/:id(.:format) toys#update
DELETE /toys/:id(.:format) toys#destroy
5. Generated *toys *controller:
[sunward@web324 x]$ rails generate controller toys
create app/controllers/toys_controller.rb
invoke erb
create app/views/toys
invoke test_unit
create test/controllers/toys_controller_test.rb
invoke helper
create app/helpers/toys_helper.rb
invoke test_unit
invoke assets
invoke coffee
create app/assets/javascripts/toys.coffee
invoke scss
create app/assets/stylesheets/toys.scss
6. Added the necessary CRUD methods to the *toys *controller:
class ToysController < ApplicationController
def index
@toys = Toy.all
end
def show
@toy = Toy.find(params[:id])
end
def new
@toy = Toy.new
end
def create
@toy = Toy.new(toy_params)
if @toy.save
redirect_to @toy
else
render 'new'
end
end
def edit
@toy = Toy.find(params[:id])
end
def update
@toy = Toy.find(params[:id])
if @toy.update(toy_params)
redirect_to @toy
else
render 'edit'
end
end
def destroy
@toy = Toy.find(params[:id])
@toy.destroy
redirect_to toys_path
end
private
def toy_params
params.require(:toy).permit(:name)
end
end
7. Made* index.html.erb, show.html.erb, new.html.erb, edit.html.erb,
_form.html.erb, index.json.jbuilder, show.json.jbuilder,* following the
pattern in http://guides.rubyonrails.org/getting_started.html.
8. Created the *Toy *model file, toy.rb:
class Toy < ActiveRecord::Base
end
9. In my browser, tried http://x.sunward.webfactional.com/toys. Feel free
to try it yourself. (However, this is a temporary site that may be gone by
the time you read this.) *It works*!!! That is, all the CRUDs execute as
they should.
10. An odd note is that there still is no *schema.rb* file in *x/db/*. If
this is what Rails uses as its "database catalog", is the lack of it going
to cause trouble down the road?
Thanks again to Scott, Hassan, & Colin for your key clues.
My next question is whether it is possible to sue the amazing Rails
generators - in particular, scaffold - to more quickly create an app that
works with an existing database - so it would not be necessary to go thru
all those manual steps shown above. I tried it once, and it tried to run
the migrator and croaked when it found that the DB table was already
there. But that may have been pilot error on my part. Comments and advice
would be welcome.
~ Ken
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