How to compare versions in Ruby?

Question

Gem::Version.new('0.4.1') > Gem::Version.new('0.10.1')

If you need to check pessimistic version constraints, you can use Gem::Dependency like this:

Gem::Dependency.new('', '~> 1.4.5').match?('', '1.4.6beta4')

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')]

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

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.

Gem::Version is the easy way to go here:

%w<0.1 0.2.1 0.44>.map {|v| Gem::Version.new v}.max.to_s
=> "0.44"