Re: referring to version numbers in a gem

On Nov 11, 2011, at 14:04 , Chad Perrin wrote:

> On Sat, Nov 12, 2011 at 05:28:15AM +0900, Chad Perrin wrote:
>> How do I specify and access a gem's version number within the code of =
the
>> gem itself?  For example:
>>=20
>> 1. I write a library.
>> 2. I write a command line utility that uses that library.
>> 3. The utility uses OptionParser, with a --version option.
>> 4. I package the things up inside a gem.
>>=20
>> What's the best way to specify the version number and give the code
>> executed when the --version argument is supplied the ability to =
access
>> that version number?
>=20
> For now, I'm going with the following.
>=20
> lib/gem_name.rb:
>=20
>    module GemName
>      @version =3D Gem::Version.new 'N.N.N'

Just use a plain string here. No reason to drag in Gem::Version at this =
point (rubygems is still pretty heavy). Also, a constant would be a =
better fit.

>      def self.version; @version; end

There's no need for a class method here. Since the version string really =
is constant (for a given install), and there isn't any morphing you're =
going to do, stick with a const.

>      . . .
>    end
>=20
> gem_name.gemspec:
>=20
>    load 'lib/gem_name.rb'
>=20
>    Gem::Specification.new do |s|
>      s.version =3D GemName.version.to_s

s.version =3D GemName::VERSION

>      . . .
>    end
>=20
> bin/gemname:
>=20
>    . . .
>=20
>      opts.on_tail('--version', help_text[:version]) do
>        puts "#{0} #{GemName.version} . . ."

puts "#{0} #{GemName::VERSION} . . ."

>      end
>    end
>=20
> If anyone sees any problems with that approach, I'd like to hear about
> it, but it seems to be working well enough for the moment.

There's nothing _wrong_ with it, but it does do a bit more than it =
needs. Using a constant in the main class/module (I don't see the value =
in separating out the version to it's own file) and then referring to =
that everywhere is the DRYest way we could come up with when we were =
figuring this stuff out. It's the pattern that hoe uses and what sow =
spits out when you create a new project with it.=