# How to generate Rails models from database schemas

**URL:** <https://www.ruby-forum.com/t/how-to-generate-rails-models-from-database-schemas/242054>\
**Category:** Rails\
**Created:** [May 22, 2015, 9:46pm UTC](https://www.ruby-forum.com/t/how-to-generate-rails-models-from-database-schemas/242054 "2015-05-22T21:46:03Z")\
**Posts on this page:** 1\
**Showing post:** 12

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**Author:** ![kenatsun](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/a9adbd/32.png) [@kenatsun](https://www.ruby-forum.com/u/kenatsun)\
**Post date:** [June 1, 2015, 2:08am UTC](https://www.ruby-forum.com/t/how-to-generate-rails-models-from-database-schemas/242054/12 "2015-06-01T02:08:10Z")

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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

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 [Getting Started with Rails — Ruby on Rails Guides](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](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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