Shuffling/Reassigning "namespaces" more easily
Push a namespace into another namespace
Consider this code here:
class Konsole; def initialize; puts 'hello world'; end; end
This may reside in a file called konsole.rb
So far so fine. Now, as more and more other projects are required,
the ruby developer may not want to have a toplevel class called
Konsole. There are other examples, such as "module Config" or
"module Configuration"; also see the change towards RbConfig, which
I assume happened to not too easily conflict with a Config namespace.
Anyway, the ruby developer would like to shuffle this namespace into
another one so that the toplevel "Konsole" goes away.
This is already possible in ruby code, I think.
We can add:
module Foobar; end
And then put Konsole into the module Foobar "namespace", possibly
so, like via this line here:
module Foobar; Konsole = ::Konsole; end
And then delete the old namespace via:
Object.send :remove_const, :Konsole
Then we can instantiate it still and I verified that this works:
konsole = Foobar::Konsole.new
The following code demonstrates this; the last line is the one
that will fail, which was what we wanted to achieve (to get
rid of toplevel class Konsole):
class Konsole; def initialize; puts 'hello world'; end; end module Foobar; end module Foobar; Konsole = ::Konsole; end Object.send :remove_const, :Konsole konsole = Foobar::Konsole.new Konsole.new
So if you look at the above code, all I am doing here is basically
to define a class and a module, and then "putting" the toplevel
class Konsole into that module "namespace"; and then using :remove_const
to get rid of the toplevel Konsole.
So far so fine, we can already do so in ruby.
But! I was thinking that this is a bit cumbersome. I am not sure if
anyone ever wants to have this, but just in the event that others
may wish to reshuffle namespaces more easily, perhaps there could
be some API to support this.
I can not think of a good name - giving things a proper name is one
of the hardest task in programming. :)
Perhaps we could add a new module called Namespace or something
for ruby 3.x or some other name. Or it could be added to Kernel or
Object, but I am not sure - it probably would not belong to either
that. Or we could have a new module where we can add lots of fancy
tricks, a bit like the old evil.rb and so forth. (Or like the
did-you-mean gem showed, with extra requires such as the
require 'did_you_mean/experimental' or require 'evil' haha, sorry,
I just like the name evil)
A few examples could be:
module Foobar; end # First we must create the new namespace. Konsole.relocate to: Foobar
Might be a good name perhaps? Not sure.
With Namespace, it could be:
Namespace.assign Konsole, to: Foobar Namespace.push Konsole, to: Foobar
Might be better, not sure.
Note that the above line, would also perform the above actions:
- Push the "namespace" Konsole into Foobar - Delete the toplevel Konsole (or, if we want to make this more general, to get rid of wherever it is defined)
Anyway! I think it may perhaps be not worth to implement this, but
I still thought that I could make the suggestion at the least.
Perhaps it also helps the generation of new, other ideas.
I assume that in the long run, with other ideas such as "isolated changes"
being possible to "namespaces" (constants), like via refinements, and matz
saying that the path to ruby 3.x is still open (aka no feature freezes and
no "idea freezes"), I thought it is ok to suggest it even if it can not
be implemented. :)
Thanks for reading!
May ruby make people happier.
I also was thinking of making this here:
Object.send :remove_const, :Foobar
Perhaps somewhat easier to read.
The last line there does not work because it is a private method. Unfortunately,
I again have the problem that I can not think of a better name either.
Or some other name.
I simply found the .send() variant a bit verbose. Anyway, I digress, I am
using it here and there. :)
Updated by kernigh (George Koehler) about 3 years ago
We can call the private method with
class Object; remove_const :Konsole; end
Your technique for moving Konsole into the Foobar namespace doesn't work if Konsole refers to itself. For example, I add code to Konsole that calls Konsole.new:
class Konsole def initialize puts 'hello world' end def another Konsole.new end end module Foobar Konsole = ::Konsole end class Object remove_const :Konsole end konsole = Foobar::Konsole.new konsole2 = konsole.another
It doesn't work...
$ ruby scratch.rb hello world scratch.rb:7:in `another': uninitialized constant Konsole::Konsole (NameError) from scratch.rb:19:in `<main>'
...because Konsole#another can't find the constant that we moved to Foobar::Konsole. This is because the definition of Konsole#another isn't inside
module Foobar; ...; end, so it doesn't search Foobar for the constant.
The same error happens with classes in the standard library, like OpenStruct:
require 'ostruct' module Foobar OpenStruct = ::OpenStruct end class Object remove_const :OpenStruct end thing = Foobar::OpenStruct.new p thing == thing
$ ruby scratch.rb /home/kernigh/prefix/lib/ruby/2.4.0/ostruct.rb:312:in `==': uninitialized constant OpenStruct::OpenStruct (NameError) from scratch.rb:11:in `<main>'
To make your feature, it isn't enough to set Foobar::OpenStruct and remove Object::OpenStruct.
Updated by matz (Yukihiro Matsumoto) about 3 years ago
- Status changed from Open to Rejected
Probably you want an isolated loading system like Java's or Python's. That's fine. It must be a good idea.
But I don't think it can be accomplished by modifying existing
require or adding anything to it.
You have to design the new one from scratch.
If you come up with any idea, please submit the proposal. That would be a nice addition to the future Ruby.