From: Charles Nutter <redmine@...>
Date: 2011-01-12T02:09:11+09:00
Subject: [ruby-core:34363] [Ruby 1.9-Feature#4264] General type coercion protocol for Ruby

Issue #4264 has been updated by Charles Nutter.


Other thoughts after talking with tenderlove:

1. double-dispatched protocol

The #to protocol could double-dispatch against the class, as in:

def to(type)
  type.coerce(self)
end

This would allow defining coercions on the target class, rather than on the #to method. It does incur the hit of doing a double-dispatch though.

2. symbolic types

Allowing a symbol could make it possible to define coercions based on name alone, such as obj.to :yaml or obj.to :json. A default impl of coerce could be added to Symbol:

class Symbol
  def coerce(obj)
    obj.send "to_#{self}"
  end
end

Given the double-dipatched protocol, the above may be left for users to implement, but it serves a similar purpose to the now-standard Symbol#to_proc.
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