From: "austin (Austin Ziegler)" Date: 2022-07-31T17:06:43+00:00 Subject: [ruby-core:109396] [Ruby master Feature#18930] Officially deprecate class variables Issue #18930 has been updated by austin (Austin Ziegler). Eregon (Benoit Daloze) wrote in #note-15: > Regarding @austin's example, there is Class#subclasses now which might be an easier way to do that. Not really, because that would require some sort of runtime filter of said subclasses. The concept I was putting together is that there are some defined *ways* of doing things that are versioned. V1 uses a random generator; V2, V3, and V4 use a timestamp generator. There���s a payload that would include an integer version number and then it would be something like `Verifier[version].verify(payload)`, where `Verifier.[]` returns the class, but *only* if it���s versioned. Using `Class#subclasses` would mean that `Verifier.[]` would need to filter based on `Class#name` matching `V#{version}`. This would be runtime looping that doesn���t work with the intended performance characteristics. > > deprecating them is just removing a tool from the programmer's toolbox > > Yes, in this case I think this is good because it's a tool which is very difficult to use correctly and can easily be replaced by clearer ways like instance variables, constants, etc. I agree that `@@vars` are *very* hard to use properly and are best deprecated with a long-term plan of removal���but I���m not as convinced that the alternative ways are *clearer*. I���ve been using Ruby for 20 years now and *still* was a little surprised when I tried what I tried and ended up with separate hierarchies. I think that, in order to deprecate them, good documentation needs to be written on how and when to use the alternatives *instead* of class variables. (This brings up a different issue, in that "how the language works" documentation is sparse and poorly organized; where is the discussion of instance variables, class instance variables, and class variables to be found in https://docs.ruby-lang.org/en/3.1/index.html?) ---------------------------------------- Feature #18930: Officially deprecate class variables https://bugs.ruby-lang.org/issues/18930#change-98547 * Author: Eregon (Benoit Daloze) * Status: Open * Priority: Normal ---------------------------------------- Ruby's class variables are very confusing, and it seem many people agree they should be avoided (#18927). How about we deprecate them officially? Concretely: * Mention in the documentation that class variables are deprecated and should be avoided/should not be used. * Add a parse-time deprecation warning, now that we only see those with `Warning[:deprecation] = true` it seems reasonable to add. -- https://bugs.ruby-lang.org/ Unsubscribe: