Feature #15374: Proposal: Enable refinements to `#method_missing`

• Status: Rejected
• Priority: Normal
• Assignee: -
• Target version: -

[osyo (manga osyo)]

Proposal enable refinements to #method_missing.
It can be used in the following cases.

# Access key value with method
using Module.new {
    refine Hash do
        # name is Symbol or String
        def method_missing(name)
            self[name.to_sym] || self[name.to_s]
        end
    end
}

hash = { name: "homu", "age" => 14 }
pp hash.name
# => "homu"
pp hash.age
# => "age"

method_missing is hard hacking.
I would like to use Refinements with method_missing.

pull request: https://github.com/ruby/ruby/pull/2036

[Hanmac (Hans Mackowiak)]

i always like the fun you can do with method_missing, but for your example, method_missing always use a symbol for the name, so name.to_sym should just return self or did you do that on purpose?

[osyo (manga osyo)]

oops, that's right.

[Eregon (Benoit Daloze)]

This wouldn't work, e.g. for hash.first, or any existing method of Hash.

Can you show a use case for this feature?

[osyo (manga osyo)]

Yes, it will be the specification of Ruby.
method_missing has a large side effect.
So can use using to control by context.

module HashWithAsscessKeyToMethod
  refine Hash do
      # name is Symbol or String
      def method_missing(name)
          self[name] || self[name.to_s]
      end
  end
end


# Do not want to use Hash#method_missing
hash = { name: "homu", age: 14 }
pp hash[:name]    # OK
# pp hash.name    # NG


# Do want to use Hash#method_missing
using HashWithAsscessKeyToMethod
pp hash.name      # OK

User can choose.

[matz (Yukihiro Matsumoto)]

• Status changed from Open to Rejected

I don't see any real-world usage of allowing #method_missing refinable. Maybe it can be used only for tricks and obfusticated code.

Matz.

[osyo (manga osyo)]

OK, Thanks matz :)