What this code means?

Ruby
1

Hello!
I am new to Ruby, can anyone explain what this code snippet is
trying to do?

module YourLastModule
class << self
def included©
class << c
def say_hellol(name)
return "Hello, " + name
end
end
end
end
end

2

2008/1/25, MohsinHijazee [email protected]:

Hello!

Hello!

I am new to Ruby, can anyone explain what this code snippet is
trying to do?

First you have to understand the following Ruby construct:

class << some_object
def hello
puts “hello”
end
end

The “class << some_object” line opens the “eigenclass”
of some_object. The eigenclass is Class object that
belongs solely to some_object and thus we’re not
interfering with any other objects class. All methods
added in “class << some_object” belong only
to some_object.

some_object.hello # prints “hello”

Now to your example:

module YourLastModule

    # At this point, self refers to YourLastModule

    # Thus here we are opening the eigenclass
    # of YourLastModule.
    class << self

       # This method is defined on the YourLastModule
       # object (and _not_ on instances of YourLastModule).
       #
       # The included method of a module is called by
       # Ruby when the module is included in a class
       # or another module. The argument c is the including
       # class or module.
       def included(c)

          # Here we open up the eigenclass of the including
          # class.
          class << c

            # Adding a method to the including class object
            # (the method is _not_ available to instances of the

class).
def say_hello(name)
return "Hello, " + name
end

          end
       end
    end

end

In effect, the example demonstrates how to add
class methods to including classes.

class Foo
include YourLastModule
end

Foo.say_hello(“Arthur”) # => “Hello, Arthur”

I’d say this stuff belongs into the advanced section
of ruby learning material.

HTH,
Stefan