Logging Changes To Database With Rails 3

Apr 7, 2011

If you’ve ever built an application that has multiple users, you might have considered adding a logging feature to keep track of modifications a user has made. So how do we do this very simply in Rails 3?

First, we need a model to store this information in. Because we are building an extremely simple logging system, we’ll just create a model that’s attached to a user and contains a small string summary of the changes that were made.

rails g model Log user_id:integer modification:string

After generating the model, you can add a simple search scope to it which allows logs to be searchable as well.

class Log < ActiveRecord::Base
  belongs_to :user
  default_scope ![:o][1] rder => "created_at DESC"

  def self.search(search)
    if search
      where(["modification LIKE ?", "%#{search}%"])
    else
      scoped
    end
  end
end

We can setup a User for has_many :logs so we can directly access a user’s actions as well.

Since we’re logging user actions, we can’t access current_user inside of a model. I don’t know the best way to do this, but what I have done, is created a simple function to log a message if the user is logged in. An after filter might be a good use for this type of functionality so you could remove these lines from the controller actions and condense them to a single function called automatically every time.

Sometimes an action may be executed by a user who isn’t signed in, this also takes care of that possibility.

  def log_action(message)
    if current_user
      l = current_user.logs.new(:modification => message)
      l.save
    end
  end

In the controller actions, you simply call it and pass in a message like so:

log_action("deleted #{visitor.first_name} #{visitor.last_name}")

This is a very simple implementation, but the end result is a nice basic searchable log of everything that has happened on the website.

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