Can't access Mysql model in rails console

Question

I have an existing remote mysql database and I am trying to access that from my rails application I have this in my database.yml development:

 development:
  adapter: mysql2
  encoding: utf8
  database: mydb
  username: myusername
  password: !@#$%@!
  host: IP for my DB
  port: 3306
  pool: 5
  socket: /tmp/mysql.sock  
  timeout: 5000

when I run the following the command in my rails console

ActiveRecord::Base.connection.tables

It list all the available tables but when I try to access the model it gives me the following error:

City
NameError: uninitialized constant City from (irb):12
    from /home/shreyas/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.11/lib/rails/commands/console.rb:47:in `start'
    from /home/shreyas/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.11/lib/rails/commands/console.rb:8:in `start'
    from /home/shreyas/.rvm/gems/ruby-1.9.3-p194/gems/railties-3.2.11/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

Any suggestions what I am doing wrong ? I want to access the remote database in my application I havent created any models as of now. Do I need to create all the models? I can see the complete db structure in my schema.rb file.

Answer 1

For that in console you can write the code like

rails g model City

it will create the City model for you. As you said, you have existing table, so you don't need the migration generated by the above syntax. So you should delete the generated migration from db/migrate.

OR else you can do one thing just add city.rb file in the app/models. Then add the code

class City < ActiveRecord::Base
   # if your table name is cities, then you don't need to do any thing.
   # if your table name is something else rather than cities then place the following commented code
   # self.table_name = 'your_existing_city_table_name'

   # then you have to add columns of the table as attr_accessible. for e.g. you have name, state_id in there
   attr_accessible :name, :state_id
end

Hope it will work for you :)

Answer 2

In case anyone comes across this, make sure to double check your models. I created them manually and forgot to allow Active Record to be aware of my models.

I had:

class Currency
  ...
end

you need to change this to show

class Currency < ApplicationRecord
  ...
end

Might save you hours of debugging :)

Answer 3

You can of course access your data inside your mysql database but in order to use it as an object representation you need to create a model associated with your data.

class City < ActiveRecord::Base
end

This way ActiveRecord will do the hard work for you in order to "link" your object to the data in your database (assuming the models name are correct, here you should have a table named cities).

You will then be able to fetch cities from rails console

City.all

For more informations on ActiveRecord, please refer to http://guides.rubyonrails.org/active_record_querying.html