How to compare versions in Ruby?

user_239895 0
Viewed 28270

How to write a piece of code to compare some versions strings and get the newest?

For example strings like: '0.1', '0.2.1', '0.44'.

ruby
8 Answers
class Version < Array
  def initialize s
    super(s.split('.').map { |e| e.to_i })
  end
  def < x
    (self <=> x) < 0
  end
  def > x
    (self <=> x) > 0
  end
  def == x
    (self <=> x) == 0
  end
end
p [Version.new('1.2') < Version.new('1.2.1')]
p [Version.new('1.2') < Version.new('1.10.1')]
user_1407400

You can use the Versionomy gem (available at github):

require 'versionomy'

v1 = Versionomy.parse('0.1')
v2 = Versionomy.parse('0.2.1')
v3 = Versionomy.parse('0.44')

v1 < v2  # => true
v2 < v3  # => true

v1 > v2  # => false
v2 > v3  # => false
user_1258440

I would do

a1 = v1.split('.').map{|s|s.to_i}
a2 = v2.split('.').map{|s|s.to_i}

Then you can do 

a1 <=> a2

(and probably all the other "usual" comparisons).

...and if you want a < or > test, you can do e.g.

(a1 <=> a2) < 0

or do some more function wrapping if you're so inclined.

user_1722110

If you want to do it by hand without using any gems, something like the following should work, though it's a little perly looking.

versions = [ '0.10', '0.2.1', '0.4' ]
versions.map{ |v| (v.split '.').collect(&:to_i) }.max.join '.'

Essentially, you turn each version string in to an array of integers and then use the array comparison operator. You could break out the component steps to get something a little easier to follow if this is going in code somebody will need to maintain.

user_906850
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