"class" return value

ruby-talk
1

All,

I noticed the following while playing in irb:

class X
def foo
4
end
end
=> nil

class Y
include Enumerable
end
=> Y

The rule appears to be that a class definition returns nil unless it includes a
mixin. Is this true, and if so, why?

Gavin

···

–
Gavin Sinclair Software Engineer
Sydney, Australia Soyabean Software Pty Ltd

2

The rule appears to be that a class definition returns nil unless it includes a
mixin. Is this true, and if so, why?

Well, in 1.6.7 `class' is a void expression, for example

pigeon% ruby -e 'a = class A; 12; end'
-e:1: void value expression
pigeon%

but

pigeon% ruby -e 'a = eval "class A; 12; end"; p a'
12
pigeon%

The class definition return the value of the last expression, `def' return
nil, `include' return the class

Guy Decoux

3

The rule appears to be that a class definition returns nil unless it
includes a
mixin. Is this true, and if so, why?

The class definition return the value of the last expression, def' return nil, include’ return the class

Guy Decoux

Thanks for the explanation, Guy.

Gavin

···

From: “ts” decoux@moulon.inra.fr