Code organization

Ruby
1

Hi all,

What are the differences bewteen the following code organization?
What situations are preferred by each one?

Thanks,

Li

#######code 1#############
module A
class B end
class C end
end

#######code 2#############
class B
include module A
end

class C
include module A
end

2

Li Chen wrote:

What are the differences bewteen the following code organization?
What situations are preferred by each one?

In code 1, module A is just acting as a namespace, so that you have two
classes, A::B and A::C. This is useful to ensure that your class names
don’t stomp on anyone else’s use of the same names. All you have to do
is ensure name A is unique.

Code 2 doesn’t run as it stands, so you need to rewrite as:

module A; end

class B
include module A
end

class C
include module A
end

In this case, instance methods defined in module A are available in both
class B and class C. This is almost the same as subclassing B and C from
class A. B and C also get access to any constants defined in the A
namespace, without needing the A:: prefix.

So in summary: they achieve two completely different ends (namespace
separation, and method sharing, respectively)

3

Brian C. wrote:

So in summary: they achieve two completely different ends (namespace
separation, and method sharing, respectively)

Hi Brian,

Thank you so much.

As I recall correctly module has two major funtions/purposes:

  1. namespace separation 2) mixin. So you mean in the second code it
    works as a mixin or method sharing?

Li

4

Li Chen [email protected] wrote:

module A

class C
include module A
end

They are totally different, and they illustrate the two main purposes of
a module. Neither is legal as you have it so I will change the code to
make it legal.

1

module A
class B
end
end
A::B.new

A is a namespace, so you must say A::B from outside module A to refer to
B.

2

module A
def hello
p “howdy”
end
end
class B
include A
end
B.new.hello

Module A’s instance methods are copied into class B as instance methods
(“mixin”).

m.

5

Li Chen wrote:

As I recall correctly module has two major funtions/purposes:

  1. namespace separation 2) mixin. So you mean in the second code it
    works as a mixin or method sharing?

Yes, mixin or method sharing (two terms to describe the same thing)

Re-reading, there’s another error I didn’t fix in that example: it
should say “include A” not “include module A”