Feature #14133


Module#{define|alias|undef}_method should be made public

Added by marcandre (Marc-Andre Lafortune) over 3 years ago. Updated over 3 years ago.

Target version:


Modules and classes can be reopened and changed (unless frozen).

This is used in many meta programming techniques.

Currently, define_method is private, so we need to either do a class_eval, reopen the class somehow, or resort to :send.

As I previously stated in #6539, I feel that the use of send should be reserved for incorrect usage of actually private methods that might change of interface or aren't meant to be called this way (e.g. respond_to_missing?, puts)

Matz has stated before that "class/module operations should be done in the scope.". Nevertheless, common usage shows that there are many cases where Rubyists prefer using a single line for this, even if it means having to call send.

Here are 95k+ examples of send :define_method in the wild:

Note that many of these are very bad usage of define_method. I feel this shows that even beginner programmers will use :send if privacy gets in the way. Let's not hinder advanced users in a failed attempt to protect the beginners.

Rails has good examples of use of send :define_method like
That's despite the fact for most metaprogramming they don't use define_method and instead build a string of code and do a module_eval for both performance and ease debugging (see the next lines in the example). That's not possible when the new methods must access blocks though, like in the example given.

alias_method and undef_method can be seen as special cases of define_method and should have the same privacy.
55k+ examples of send :alias_method in the wild:
30k+ examples of send :undef_method in the wild:
20k+ examples of send :remove_method in the wild:

Related issues

Related to Ruby master - Feature #14132: Module#attr{|_reader|_writer} should be publicClosedmatz (Yukihiro Matsumoto)Actions
Related to Ruby master - Feature #6539: public and private for core methodsClosednobu (Nobuyoshi Nakada)Actions

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