From: Gavin Kistner <gavin@...>
Date: 2005-10-02T03:09:11+09:00
Subject: Better way to make struct with defaults?

I'm using the same ideas as Struct to quickly create a class that:
a) Has default values for the properties
b) Uses symbols inside #new to set the values (instead of argument  
order)

I have it working (code below) but whenever I construct a string for  
use with *_eval, I feel that I'm probably being boneheaded, and  
there's a better way to do it. What suggestions do people have for  
cleaning up and/or simplifying the following code?

def Struct.with_defaults( property_hash )
     klass = self.new( *property_hash.keys )
     klass.class_eval <<-ENDCODE
         def initialize( values={} )
             #{property_hash.map{ |prop,default|
                 "self.#{prop} = values[#{prop.inspect}] || # 
{default.inspect}"
             }.join("\n")}
         end
     ENDCODE
     klass
end

Person = Struct.with_defaults :sex=>'male', :age=>0, :name=>nil
gk = Person.new :name=>'Gavin', :age=>32
p gk
#=> #<struct Person sex="male", name="Gavin", age=32>