Can't get class name

Ruby
1

I am learning how to design a DSL by using const_missing, but I face a
problem on getting class name:

class Drawing
def initialize(&block)
instance_eval(&block)
end

def self.const_missing(constant)
klass = Class.new do
def self.<(super_klass)
puts “#{self.name} inherits from #{super_klass.name}”
end

  def self.-(association_klass)
    puts "#{self.name} has association with

#{association_klass.name}"
end
end

const_set(constant, klass)

end
end

Drawing.new do
Student < Person
Student - Courses
end

Output:
inherits from
has association with

Expected output:
Student inherits from Person
Student has association with Courses

2

On Tue, Jan 4, 2011 at 6:29 PM, Samnang C. [email protected]
wrote:

I am learning how to design a DSL by using const_missing, but I face a
problem on getting class name:

I am not sure what you are attempting. But you should keep these facts
in mind:

  1. You cannot change inheritance of a class after creation.

  2. A class has a name only after const assignment.

11:11:21 Temp$ ruby19 -e ‘c=Class.new;p c, c.name;A=c;p c, c.name’
#Class:0x1005309c
nil
A
“A”

11:12:50 Temp$ ruby19 -e ‘c=Class.new;p c,
c.name;Object.const_set(“A”,c);p c, c.name’
#Class:0x1005304c
nil
A
“A”

class Drawing
def initialize(&block)
instance_eval(&block)
end

def self.const_missing(constant)
klass = Class.new do
def self.<(super_klass)
puts “#{self.name} inherits from #{super_klass.name}”
end

Bad idea IMHO: Class#< is defined already with particular semantics
(inheritance check):

11:13:59 Temp$ ruby19 -e ‘p Array < Enumerable’
true

Also, as I said, you cannot change inheritance after creation of a
class.

Drawing.new do
You are creating an instance of Drawing while you probably rather want
constants Student, Person etc. set in class Drawing.

Student has association with Courses
Try this to see what’s happening:

class Drawing
def initialize(&block)
instance_eval(&block)
end

def self.const_missing(constant)
p [self, constant]

klass = Class.new do
def self.<(super_klass)
# puts “#{self.name} inherits from #{super_klass.inspect}”
printf “%p < %p\n”, self, super_klass
end

 def self.-(association_klass)
   # puts "#{self.name} has association with

#{association_klass.inspect}"
printf “%p - %p\n”, self, association_klass
end
end

def klass.x(cl)
printf “%p x %p\n”, self, cl
end

const_set(constant, klass)
end
end

Drawing.new do
Student < Person
Student - Courses
Student.x Foo
end

p Drawing.constants

class Drawing
Student < Person
Student - Courses
Student.x Foo
end

p Drawing.constants

Kind regards

robert