Propogate variable up to included module

Ruby
1

Hey folks,

I have a module which I’m using to contain a lot of strings that my
objects print out. I want to use a module because it seems better to me
to put the data in a separate location than my object implementation, so
I can more easily see the logic of my object.

My object builds a set of text files. Each of these text files has
sections within them that are customised based upon a string handed in
to the object, such that:

bill = textFile.new(“bill”)

bill.header #returns “This is the header for bill”
bill.comment #returns “Bill is implemented with the following options:”
followed by the unique options for bill.

ted = textFile.new(“ted”)
ted.header #returns “This is the header for ted”
ted.comment #returns “ted is implemented with the following options:”
followed by the unique options for ted.

and so on.

Now, what I want is to have my Textfile class include a data module. The
data module contains all of the strings “This is the header for
#{variable}”, “#{variable} is implemented with the following options:”.

As such, I need to pass the argument to the textfile’s new method back
up into the module that the textfile includes.

I guess the question is, is there a way to reference a variable from a
class in a module that the class will include?

Thanks

2

On May 14, 2:34 pm, James H. [email protected] wrote:

class in a module that the class will include?
At the instance level yes, and the module level no (though you can
work around).

Instance level:

module M
def m
@x
end
end

class X
include M
def initialize
@x = 10
end
end

X.new.m #=> 10

Class level (trick):

module M
def self.m
@x ||= 20
end
end

class X
include M
def self.m
anc = ancestors.find{ |a| a.respond_to?(:m) }
anc.m if anc
end
end

trans.

3
module M > def self.m > @x ||= 20 > end > end I do not think this is necessary > > class X > include M > def self.m > anc = ancestors.find{ |a| a.respond_to?(:m) } > anc.m if anc replace this with instance_variable_get (potentially guarded by an instance_variable_defined?)

I wonder however, what this is good for, I am not sure I understood
what OP wanted
HTH
R.

4

On May 15, 1:05 pm, Robert D. [email protected] wrote:

def self.m
anc = ancestors.find{ |a| a.respond_to?(:m) }
anc.m if anc

replace this with instance_variable_get (potentially guarded by an
instance_variable_defined?)

How would that work?

I wonder however, what this is good for, I am not sure I understood
what OP wanted

Basically class inheritable attributes.

5

On Sat, May 15, 2010 at 7:24 PM, Intransition [email protected]
wrote:

I wonder however, what this is good for, I am not sure I understood
what OP wanted

Basically class inheritable attributes.

That’s exactly what I gave you, good then :slight_smile:
Cheers
R.

6

Basically class inheritable attributes.

I thought modules sit further up the inheritance chain that classes?
This isn’t a case of inheriting down, this is a case of propagating back
up the chain.

It’s entirely possible I misunderstand, but Metaprogramming Ruby
definitely indicates that a module will sit above a class in an
inheritance chain.