From: Tanaka Akira <akr@...17n.org>
Date: 2002-02-02T15:10:22+09:00
Subject: [ruby-dev:15841] abstract method

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class AbstractMethodCallError < NotImplementedError
end

class Module
  AbstractMethods = {}

  def define_abstract_method(name)
    name = name.to_s.intern unless Symbol === name
    AbstractMethods[self] ||= []
    AbstractMethods[self] << name
    self.class_eval {
      define_method(name) {raise AbstractMethodCallError.new(name.to_s)}
    }
  end

  def abstract_methods
    methods = []
    ancestors.reverse_each {|mod|
      methods -= mod.instance_methods.map {|name| name.intern}
      methods |= AbstractMethods[mod] if AbstractMethods.include? mod
    }
    methods
  end

  def abstract?
    !abstract_methods.empty?
  end
end

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  class A
    define_abstract_method :a
    ...
  end

  class C < A
    ...
  end

  if __FILE__ == $0
    ...
        assert_equal([], C.abstract_methods)
    ...
  end

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-- 
[$BEDCf(B $BE/(B][$B$?$J$+(B $B$"$-$i(B][Tanaka Akira]
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