Re: Modifying Struct members

here we go:

#!/usr/bin/ruby -w

require 'rubygems'
require 'inline'

class Object
  inline :C do |builder|
    builder.c "VALUE thaw() { FL_UNSET(self, FL_FREEZE); return  
self; }"
  end
end

class Struct
  inline :C do |builder|
    builder.c_singleton "
      void raw_members() {
        return rb_struct_s_members(self);
      }
    "

    builder.c_singleton '
       void set_s_size(long n) {
         rb_iv_set(self, "__size__", LONG2NUM(n));
       }
    ', :method_name => :size=

    builder.c '
       void set_size(long n) {
         RSTRUCT(self)->len = n;
       }
    ', :method_name => :size=
  end

  def self.add_member name
    self.raw_members.thaw
    self.raw_members << name

    # a bit hacky, but works
    self.send(:define_method, name)       {     self[name]     }
    self.send(:define_method, "#{name}=") { |o| self[name] = o }

    new_size =  self.raw_members.size
    self.size = new_size

    ObjectSpace.each_object(self) do |o|
      o.size = new_size
    end
  end
end

Thing = Struct.new(:a, :b, :c) do
  def some_thing
  end
end

t = Thing.new(1, 2, 3)

p [t.a, t.b, t.c]
# => [1, 2, 3]

Thing.add_member :d

t.d = 4 # t['d'] = 4 works just as well now

p(('a'..'d').map { |c| t[c] })
# => [1, 2, 3, 4]
p(('a'..'d').map { |c| t.send c })
# => [1, 2, 3, 4]