A Ruby class is very similar to the other programming languages class
structures. They allow for code to be created within a single object that
can be reused etc, the code can have its own separate block of
variables/methods for that instance of the required task. It is able to be
inherited and extended which is different to a module which only allows for
the created module to have methods and constant variables.
module SillyModule # module is a single instance object, e.g. they can have
methods and constants
def hello
"Hello."
end
end
class SillyClass # a class can include a module and expand on it, an class
can generate many instances (objects) of itself.
include SillyModule # also use the sillymodule as well.
def bob
"timing is everything."
end
end
s = SillyClass.new
puts s.hello # Hello.
puts s.class # SillyClass - displays the class name
puts s.bob # timing is everything
Save this code as class_module.rb, it will create a module that is included
within the SillyClass. To demonstrate that the module is a single instance
of a object, if you try to create a new object, e.g. mod = SillyModule.new,
the compile will
class.rb:20: undefined method `new' for SillyModule:Module (NoMethodError)
since the new method is not part of a module but only a class. |
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