Hmm. Okay, first a bunch of thoughts, then some potential solutions.
1. Variables that begin with the $ sigil are global. For a local variable,
no sigil necessary:
module Foo
def setup
@foo = self.object_id
end
def foo
return @foo
end
end
class Bar
include Foo
end
bar_one = Bar.new
bar_one.setup
bar_one.foo # => 2151888860
2. There is an implicit setup method called "initialize", it is unusual to
me that you have your own, which you invoke explicitly.
module Foo
def initialize
@foo = self.object_id
end
def foo
return @foo
end
end
class Bar
include Foo
end
Bar.new.foo # => 2151889080
3. When invoking a method on the current object, self is not necessary
module Foo
def initialize
@foo = object_id
end
def foo
return @foo
end
end
class Bar
include Foo
end
Bar.new.foo # => 2151889080
4. The last line of a method is automatically returned, no explicit "return"
is necessary
module Foo
def initialize
@foo = object_id
end
def foo
@foo
end
end
class Bar
include Foo
end
Bar.new.foo # => 2151889100
5. When you have a method which returns an instance variable of the same
name, that is a less efficient version of "attr_reader :ivar_name"
module Foo
def initialize
@foo = object_id
end
attr_reader :foo
end
class Bar
include Foo
end
Bar.new.foo # => 2151889260
···
On Sat, May 7, 2011 at 10:02 PM, Geometric Patterns < geometric.patterns@gmail.com> wrote:
Hi,
In the code below, is there a way to learn @foo from $bar_one
using $bar_two?
Many thanks in advance!!
----------------
#!/usr/bin/ruby -w
module Foo
def setup
@foo = self.object_id
end
def foo
return @foo
end
end
class Bar
include Foo
end
$bar_one = Bar.new
$bar_one.setup
p $bar_one.foo # => 2148224640
$bar_two = Bar.new
p $bar_two.foo # => warning: instance variable @foo not initialized
----------------
--
Posted via http://www.ruby-forum.com/\.
---
Okay, now that we're here, I assume you want to know if bar_two can know
bar_one's foo
bar_one = Bar.new
bar_two = Bar.new
bar_one.foo # => 2151886760
bar_two.foo # => 2151886740
But it is unclear, because you were initially using global variables, which
breaks scope, allowing a method like
module Foo
def initialize
@foo = object_id
end
attr_reader :foo
def bar_ones_foo
$bar_one.foo
end
end
class Bar
include Foo
end
$bar_one = Bar.new
$bar_two = Bar.new
$bar_one.foo # => 2151884160
$bar_two.foo # => 2151884140
$bar_two.bar_ones_foo # => 2151884160
Which, seems very strange to me, and doesn't work if you actually meant to
have local variables (globals are considered a code smell).
Alternatively, you could have been asking whether they could share the @foo
ivar, in which case the answer is no, that ivar is unique to whichever
object the method is being called on. However, you could use a class
variable
module Foo
def initialize
@@foo = object_id
end
def foo
@@foo
end
end
class Bar
include Foo
end
bar_one = Bar.new
bar_one.foo # => 2151892400
bar_two = Bar.new
bar_two.foo # => 2151891900
bar_one.foo # => 2151891900
Foo.class_variables # => [:@@foo]
Or, more commonly, an instance variable either on Foo or on Bar
module Foo
class << self
attr_accessor :foo
end
def initialize
Foo.foo = object_id
end
def foo
Foo.foo
end
end
class Bar
include Foo
end
bar_one = Bar.new
bar_one.foo # => 2151891940
bar_two = Bar.new
bar_two.foo # => 2151891440
bar_one.foo # => 2151891440
Although, your wording is pretty vague, this would technically satisfy the
request
module Foo
def initialize
@foo = object_id
end
attr_reader :foo
def foo_of(other)
other.foo
end
end
class Bar
include Foo
end
bar_one = Bar.new
bar_two = Bar.new
bar_one.foo # => 2151894400
bar_two.foo # => 2151894380
bar_two.foo_of bar_one # => 2151894400
So anyway, hopefully something in there addresses what you are asking. If
not, you'll have to give more feedback (ie an interface to access this
information).