auto_increment

auto_increment provides automatic incrementation for a integer or string fields in Rails.

Installation

You can use auto_increment as a gem in Rails 4.

To use the gem version, put the following gem requirement in your Gemfile:

gem "auto_increment"

To work with a auto increment column you used to do something like this in your model:

before_create :set_code
def set_code
  max_code = Operation.maximum(:code)
  self.code = max_code.to_i + 1
end

Looks fine, but not when you need to do it over and over again. In fact auto_increment does it under the cover.

All you need to do is this:

auto_increment :code

And your code field will be incremented

So you have a different column or need a scope. auto_increment provides options. You can use it like this:

auto_increment :letter, scope: [:account_id, :job_id], initial: 'C', force: true, lock: false

First argument is the column that will be incremented. Can be integer or string.

scope: you can define columns that will be scoped and you can use as many as you want (default: nil)
initial: initial value of column (default: 1)
force: you can set a value before create and auto_increment will not change that, but if you do want this, set force to true (default: false)
lock: you can set a lock on the max query. (default: false)

Tested with Rails 4.2.2 in Ruby 2.0.0