Adds fine-grained visibility semantics to Ruby, allowing you to make methods visible only to specific classes (and their subclasses).

$ [sudo] gem install friend

Or build it manually:

$ git clone git:https://github.com/lsegal/friend
$ cd friend
$ rake install

To use the library, require it and call friend (aka. export) from any module/class to export a method to a list of specific classes in the form:

export :methodname, Class1, Class2, ...

Note: export is an alias of friend. They do the exact same thing, though depending on your semantics one terminology might be more suited than the other.

require 'friend'

class A; def bar; D.new.foo end end
class B; def bar; D.new.foo end end
class C; def bar; D.new.foo end end

class D
  def foo; "HELLO WORLD!" end

  # Export to A and B, but not C
  export :foo, A, B 
end

puts A.new.bar
puts B.new.bar
puts C.new.bar

# Output:
# 
# HELLO WORLD!
# HELLO WORLD!
# export_features.rb:5:in `bar': `foo' is not accessible to C:Class (NoMethodError)
#   from export_features.rb.rb:16:in `<main>'

More examples can be found in the example/ directory.

Friend is written by Loren Segal © 2010, licensed under the BSD license. This software can be redistributed and modified so long as it maintains the copyright notice and LICENSE file. See LICENSE for more information.