Packer

Require different versions of the same Cargo-compatible gem.

Cargo lets you import two versions of the same library, and Packer brings the same functionality to Cargo-compatible gems.

Consider these two versions of the same library:

$ gem list

*** LOCAL GEMS ***

par (0.0.2)
par (0.0.1)

You can now load both versions side by side:

>> Par1 = package("par", "= 0.0.1")
=> #<Module:0x000001009ffa28>::Par
>> Par2 = package("par", "= 0.0.2")
=> #<Module:0x000001009f2828>::Par
>> Par1::VERSION
=> "0.0.1"
>> Par2::VERSION
=> "0.0.2"

First, check how Cargo works. Packer just combines Cargo with RubyGems.

After requiring packer in the calling program, the methods package, import and export become available. Both import and export come from Cargo, and package is defined in Packer.

This is how you use package in the calling program:

require "packer"

MyFoo = package("foo", "= 1.0.0")

And for that to work, the imported gem should look like this:

class Foo
  VERSION = "1.0.0"
end

export(Foo)

$ gem install packer