How to compare versions in Ruby?

Question

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\'.

Answer 1

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.

Answer 2

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')]

Answer 3

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.

Answer 4

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

Answer 5

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

Answer 6

I had the same problem, I wanted a Gem-less version comparator, came up with this:

def compare_versions(versionString1,versionString2)
    v1 = versionString1.split('.').collect(&:to_i)
    v2 = versionString2.split('.').collect(&:to_i)
    #pad with zeroes so they're the same length
    while v1.length < v2.length
        v1.push(0)
    end
    while v2.length < v1.length
        v2.push(0)
    end
    for pair in v1.zip(v2)
        diff = pair[0] - pair[1]
        return diff if diff != 0
    end
    return 0
end