Re: Help with object scope


#1

module M
class C
def self.blah
end
end
end

module M2
include M
class TestM
def setup; C.blah; end
end
end

Won’t work because the C tries to refer to TestM::C, which doesn’t
exist.

Previously, when you did an “include M” you included the module into
Kernel.

Since:
TestM is an instance of Class
Class is an instance of Object
You’ve included M in Object, causing Object::C to be created

So, in that case TestM::C exists.

I had a file, in short:
end

Works great.

However, if I wrap the unit tests in their own module, then
ruby can
no longer find class C. Why? Didn’t I include module M? I’m really
confused here.

If you want the full source, I can post it.
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#2

I see.

So,

  1. How do I call C from class TestM without explicitly using its
    namespace (M:C)? Is there no way? I don’t want to modify Kernel or
    anything, just have class C available.

  2. Could you explain exactly what a Module is? A namespace? A set of
    methods without a home? I’m really confused… (I know that
    module_define and class_define are synonomous, which is even more
    confusing…)

Daniel S. wrote:

module M
class C
def self.blah
end
end
end

module M2
include M
class TestM
def setup; C.blah; end
end
end

Won’t work because the C tries to refer to TestM::C, which doesn’t
exist.

Previously, when you did an “include M” you included the module into
Kernel.

Since:
TestM is an instance of Class
Class is an instance of Object
You’ve included M in Object, causing Object::C to be created

So, in that case TestM::C exists.

I had a file, in short:
end

Works great.

However, if I wrap the unit tests in their own module, then
ruby can
no longer find class C. Why? Didn’t I include module M? I’m really
confused here.

If you want the full source, I can post it.
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#####################################################################################
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#3

List R. wrote:

  1. Could you explain exactly what a Module is? A namespace? A set of
    methods without a home? I’m really confused… (I know that
    module_define and class_define are synonomous, which is even more
    confusing…)

A little bit of both, actually. Here’s a good description of what a
Module is: http://www.rubycentral.com/book/tut_modules.html


#4

List R. wrote:

So,

  1. How do I call C from class TestM without explicitly using its
    namespace (M:C)? Is there no way? I don’t want to modify Kernel or
    anything, just have class C available.

Try this instead:

class TestM
include M
def setup; C.blah; end
end

A module is a set of instance methods and constants. It can either be
used as a namespace or mix-in functionality. (For the latter you are
collecting similar methods / constants together in one Module so you can
add them to your own classes or objects easily.)

mod_or_cls.include(mod) will add all constants and instance methods of
mod to mod_or_cls.

obj.extend(mod) will add all constants and instance methods of mod to an
object itself.

Here’s a sample:

module HalfString
def half()
self[0, length / 2]
end
end

str = “foobar”
str.half() # raises NoMethodError
str.extend(HalfString)
str.half() # => “foo”

“hello”.half() # raises NoMethodError

You can’t ever include classes. You can only inherit from them.


#5

Try this instead:

class TestM
include M
def setup; C.blah; end
end

I see.

So, that’s the equivalent of:

class TestM
class C; … ; end
def setup; C.blah ; end
end

What exactly does it mean to nest a class?
I know that you cannot define a class within a method (not sure why)?

Also, is require the same thing as “copy and paste dynamically”, or does
it drop down to the global namespace, or do something else?