Constants defined within a class or module may be accessed unadorned
anywhere within the class or module.
Outside the class or module, they
may be accessed using the scope operator, ``
::'' prefixed by an
expression that returns the appropriate class or module object.
Constants defined outside any class or module may be accessed
unadorned or by using the scope operator ``
::'' with no prefix. Constants may not
be defined in methods.
OUTER_CONST = 99
|
class Const
|
def getConst
|
CONST
|
end
|
CONST = OUTER_CONST + 1
|
end
|
Const.new.getConst
|
� |
100
|
Const::CONST
|
� |
100
|
::OUTER_CONST
|
� |
99
|
Global variables are available throughout a program. Every reference
to a particular global name returns the same object. Referencing an
uninitialized global variable returns
nil.
Class variables are available throughout a class or module body. Class
variables must be initialized before use. A class variable is shared
among all instances of a class and is available within the class
itself.
class Song
@@count = 0
def initialize
@@count += 1
end
def Song.getCount
@@count
end
end
|
Class variables belong to the innermost enclosing class or
module. Class variables used at the top level are defined in
Object, and behave like global variables. Class variables defined
within singleton methods belong to the receiver if the receiver is a
class or a module; otherwise, they belong to the class of the receiver.
class Holder
@@var = 99
def Holder.var=(val)
@@var = val
end
end
a = Holder.new
def a.var
@@var
end
|
