Create a package based upon a Gem::Specification. Gem packages, as well as zip files and tar/gzipped packages can be produced by this task.

In addition to the Rake targets generated by Rake::PackageTask, a Gem::PackageTask will also generate the following tasks:

“package_dir/name-version.gem”

Create a RubyGems package with the given name and version.

Example using a Gem::Specification:

require 'rubygems'
require 'rubygems/package_task'

spec = Gem::Specification.new do |s|
  s.summary = "Ruby based make-like utility."
  s.name = 'rake'
  s.version = PKG_VERSION
  s.requirements << 'none'
  s.files = PKG_FILES
  s.description = <<-EOF
Rake is a Make-like program implemented in Ruby. Tasks
and dependencies are specified in standard Ruby syntax.
  EOF
end

Gem::PackageTask.new(spec) do |pkg|
  pkg.need_zip = true
  pkg.need_tar = true
end
Methods
D
I
N
Attributes
[RW] gem_spec

Ruby Gem::Specification containing the metadata for this package. The name, version and package_files are automatically determined from the gemspec and don't need to be explicitly provided.
Class Public methods
new(gem_spec)

Create a Gem Package task library. Automatically define the gem if a block is given. If no block is supplied, then define needs to be called to define the task.

Source: show | on GitHub 

# File lib/rubygems/package_task.rb, line 77
def initialize(gem_spec)
  init gem_spec
  yield self if block_given?
  define if block_given?
end
Instance Public methods
define()

Create the Rake tasks and actions specified by this Gem::PackageTask. (define is automatically called if a block is given to new).

Source: show | on GitHub 

# File lib/rubygems/package_task.rb, line 96
def define
  super

  gem_file = File.basename gem_spec.cache_file
  gem_path = File.join package_dir, gem_file
  gem_dir  = File.join package_dir, gem_spec.full_name

  task :package => [:gem]

  directory package_dir
  directory gem_dir

  desc "Build the gem file #{gem_file}"
  task :gem => [gem_path]

  trace = Rake.application.options.trace
  Gem.configuration.verbose = trace

  file gem_path => [package_dir, gem_dir] + @gem_spec.files do
    chdir(gem_dir) do
      when_writing "Creating #{gem_spec.file_name}" do
        Gem::Package.build gem_spec

        verbose trace do
          mv gem_file, '..'
        end
      end
    end
  end
end
init(gem)

Initialization tasks without the “yield self” or define operations.

Source: show | on GitHub 

# File lib/rubygems/package_task.rb, line 86
def init(gem)
  super gem.full_name, :noversion
  @gem_spec = gem
  @package_files += gem_spec.files if gem_spec.files
end