From: Clifford Heath <no.spam@...>
Date: 2007-01-31T15:30:13+09:00
Subject: Re: Tricks with method as superclass

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ara.t.howard@noaa.gov wrote:
>       # Class.new(Foo).instance_eval <<-END
>       Class.new(Foo).module_eval <<-END

Thanks Ara - super-quick response too! Caught out by the singleton,
which I didn't expect to find on a Class instance. Here's a complete
example that shows most of what's possible, assuming the attachment
comes through.

Clifford Heath.

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# Start with a real base class
class Base
    def initialize(*args, &block)
	# puts "Base::initialize #{args.inspect} &#{block.inspect}"
	print("Base::")
	block.call(*args) if block
    end

    # Return a new anonymous class derived from Base, with class variables and initialize
    def self.augment(*args, &block)
	Class.new(self).class_eval {
	    @@_base_args = args
	    @@_base_block = block
	    # puts "new class is #{self.object_id} #{args.inspect} &#{block.inspect}"

	    def initialize(*args, &block)
		# puts "Constructing instance with base #{@@_base_args.inspect} &#{@@_base_block.inspect}, instance #{args.inspect} &#{block.inspect}"
		@@_base_block.call(*@@_base_args) if @@_base_block
		super(*args, &block)
	    end

	    self
	}
    end
end

# Here's the method used to create the custom base class:
def Base(*args, &block)
    puts "Defining funky magic with #{args.inspect} &#{block.inspect}"

    Base.augment(*args, &block)
end

# A subclass with neither args nor block:
class Sub0 < Base
end
Sub0.new { puts "No augmented class, use Base alone" }

# A subclass with just args:
class Sub1 < Base("arg1")
end
Sub1.new("Thinking...") { |*args| puts "#{args.inspect}: Ok" }

# A subclass with just a block:
class Sub2 < Base { print "Hi" }
end
Sub2.new { puts " there!" }

# A subclass with args and a block:
class Sub3 < Base("arg1", "arg2") { |*args|
	puts "#{args.inspect}: getting things all ready for you..."
    }

    def initialize(*args, &block)
	super(*args, &block)

	puts "#{args.inspect}: fun for all the family!"
    end
end

Sub3.new("sub1", "sub2") { |*args|
	puts "#{args.inspect}: still working"
    }

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