Keywords and Identifiers
The keywords (or reserved words) in Ruby typically cannot be used for other purposes. These are as follows:
| BEGIN |
END |
alias |
and |
begin |
| break |
case |
class |
def |
defined |
| do |
else |
elsif |
end |
ensure |
| false |
for |
if |
in |
module |
| next |
nil |
not |
or |
redo |
| rescue |
retry |
return |
self |
super |
| then |
true |
undef |
unless |
until |
| when |
while |
yield |
|
|
Variables and other identifiers normally start with an alphabetic letter or a special modifier. The basic rules are as follows:
-
Local variables (and pseudo-variables such as self and nil) begin with a lowercase letter.
-
Global variables begin with a dollar sign ($).
-
Instance variables (within an object) begin with an "at" sign (@).
-
Class variables (within a class) begin with two "at" signs (@@).
-
Constants begin with capital letters.
For purposes of forming identifiers, the underscore (_) may be used as a lowercase letter. Special variables starting with a dollar sign (such as $1 and $/) are not dealt with here.
The following list provides some examples:
-
Local variables: alpha, _ident, some_var
-
Pseudo-variables: self, nil, __FILE__
-
Constants: K6chip, Length, LENGTH
-
Instance variables: @foobar, @thx1138, @NOT_CONST
-
Class variable: @@phydeaux, @@my_var, @@NOT_CONST
-
Global variables: $beta, $B12vitamin, $NOT_CONST
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