Defining a class without opening an existent one

Ruby
1

Hi there!

I want to define a class which happens to have the same name as a
builtin class. It shouldn’t be a problem because it’s in an extra
namespace, but Ruby opens the existing class instead of defining a new
one. Here’s an example:

module MyNamespace
class Array
# Some stuff
end
end

I tried using the full qualifier (class MyNamespace::Array) but it
didn’t help. Is there a possibility to actually define a new class?

2

Hagbard C. wrote:0

I want to define a class which happens to have the same name as a
builtin class. It shouldn’t be a problem because it’s in an extra
namespace, but Ruby opens the existing class instead of defining a new
one. Here’s an example:

module MyNamespace
class Array
# Some stuff
end
end

That’s fine. What makes you think that this didn’t create a separate
class?

I tried using the full qualifier (class MyNamespace::Array) but it
didn’t help.

In what way didn’t it help? Did you get an error message? Post your full
code and the exception.

Is there a possibility to actually define a new class?

Sure, you’ve just done it :slight_smile:

module MyNamespace; class Array; end; end
=> nil

Array.object_id
=> 70098182563360

MyNamespace::Array.object_id
=> 70098182326040

a = MyNamespace::Array.new
=> #MyNamespace::Array:0x7f820281f520

a[1]
NoMethodError: undefined method `[]’ for
#MyNamespace::Array:0x7f820281f520
from (irb):5
from :0

3

All of a sudden, the scales fall from my eyes. At first I wasn’t so sure
whether I defined a new class or not myself. I looked at the methods of
the class and something made me think that they were the same as
Arrays. Retrospectively, I don’t know what made me think so. Thanks
for your help.

4

Robert K. wrote:

creation of a class with the same name as one of
the core classes does not seem like a good idea to me - although it’s
certainly possible. It may cause confusion and it also makes using
the core class more cumbersome (you need to reference it as ::Array in
the module and nested classes for example).

That’s true but unfortunately Array is just the perfect name for my
class. I rather use MyNamespace::Array and ::Array instead of inventing
a bad-fitting name for the class.

5

On Thu, Sep 23, 2010 at 9:59 PM, Hagbard C. [email protected]
wrote:

All of a sudden, the scales fall from my eyes. At first I wasn’t so sure
whether I defined a new class or not myself. I looked at the methods of
the class and something made me think that they were the same as
Arrays. Retrospectively, I don’t know what made me think so. Thanks
for your help.

Just adding 0.02EUR: creation of a class with the same name as one of
the core classes does not seem like a good idea to me - although it’s
certainly possible. It may cause confusion and it also makes using
the core class more cumbersome (you need to reference it as ::Array in
the module and nested classes for example).

Kind regards

robert