CODEWITHSUNDEEP
ruby-on-railsdatabase-migration
Ahmad Al-kheat
Ahmad Al-kheat

Reputation: 1795

Trying to convert existing IPS to integers

I have a users table that contains a bunch of IPS in string format, now we decided to start storing IPS as integers, so I added this piece of code to my user.rb model : 

class User < ActiveRecord::Base
  [:current_sign_in_ip, :last_sign_in_ip].each do |field|
    define_method(field) do
      ip = read_attribute(field)
      return nil unless ip
      ip += 4_294_967_296 if ip < 0 # Convert from 2's complement
      "#{(ip & 0xFF000000) >> 24}.#{(ip & 0x00FF0000) >> 16}.#{(ip & 0x0000FF00) >> 8}.#{ip & 0x000000FF}"
    end

    define_method("#{field}=") do |value|
      quads = value.split('.')
      if quads.length == 4
        as_int = (quads[0].to_i * (2**24)) + (quads[1].to_i * (2**16)) + (quads[2].to_i * (2**8)) + quads[3].to_i
        as_int -= 4_294_967_296 if as_int > 2147483647 # Convert to 2's complement
      else
        as_int = nil
      end
      write_attribute(field, as_int)
    end

  end
end

This code works fine, when a new user registers, his/her IP will be stored as integer. Now I need to create a migration that will change the type of the IP columns from string to integer :

class ConvertStringIpsToIntegers < ActiveRecord::Migration

def up

  change_column :users, :current_sign_in_ip, :integer
  change_column :users, :last_sign_in_ip,    :integer
end

def down
  change_column :users, :current_sign_in_ip, :string
  change_column :users, :last_sign_in_ip,    :string
end

end

However this migration will destroy the old IPS that were stored as strings "127.0.0.1" will become 127 after the migration. Any idea how I can convert all existing IPS from strings to integers before running the migration?

Thanks

Upvotes: 0

Views: 95

Answers (1)

SteveTurczyn
SteveTurczyn

Reputation: 36860

You can include your conversion code in a migration. Do the actual conversion from string into integer in a separate conversion.

def up
  User.all.each do
    [:current_sign_in_ip, :last_sign_in_ip].each do |field|
      quads = user.read_attribute(field).split('.')
      if quads.length == 4
        as_int = (quads[0].to_i * (2**24)) + (quads[1].to_i * (2**16)) + (quads[2].to_i * (2**8)) + quads[3].to_i
        as_int -= 4_294_967_296 if as_int > 2147483647 # Convert to 2's complement
      else
        as_int = nil
      end
      user.write_attribute(field, "#{as_int}")
    end
  end
end

def down
  User.all.each do |user|
    [:current_sign_in_ip, :last_sign_in_ip].each do |field|
      ip = user.read_attribute(field).to_i
      return nil unless ip
      ip += 4_294_967_296 if ip < 0 # Convert from 2's complement
      user.write_attribute(field, "#{(ip & 0xFF000000) >> 24}.#{(ip & 0x00FF0000) >> 16}.#{(ip & 0x0000FF00) >> 8}.#{ip & 0x000000FF}")
    end
  end
end

Upvotes: 1

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