Inherited question

ruby-talk
1

I’m playing around with the inherited hook and I’m having some problems.
The following code is running on “ruby 1.6.7 (2002-03-19) [i386-linux]”.
It works fine when I leave the inherited def out, and explicitly register
the child class. However, if I attempt the same with the hook, I get the
following error:

check-inherited.rb:9:in initialize': wrong # of arguments(0 for 1) (ArgumentError) from check-inherited.rb:9:in new’
from check-inherited.rb:9:in register' from check-inherited.rb:5:in inherited’
from check-inherited.rb:20

check-inherited.rb

class Base
@@childitems = {}

def self.inherited(subclass)

self.register(subclass)

end

def self.register(subclass)
item = subclass.new
@@childitems[item.name] = item
end

attr_reader :name

def initialize(name)
@name = name
end
end

class Sub1 < Base
def initialize
super(‘child_sub1’)
end
end

not called when testing with self.inherited commented-in

Base.register(Sub1)

end of file

···

–
Alan Chen
Digikata LLC

2

Class#inherited would be called when the line “class Sub1 < Base” is
evaluated. In the time, Base#initialize is not defined yet and the
arity (i.e. # of args) of Sub1.new is 1, which is same to Base.new’s
because the arity of Base#initialize is 1.

The following sketches the problem.

class A
def initialize(x) end
end

class B < A
end

p B.new # uncomment and will get ArgumentError

class B
def initialize() end
end

p B.new

– Gotoken

···

At Thu, 8 Aug 2002 04:17:17 +0900, Alan Chen wrote:

I’m playing around with the inherited hook and I’m having some problems.
The following code is running on “ruby 1.6.7 (2002-03-19) [i386-linux]”.
It works fine when I leave the inherited def out, and explicitly register
the child class. However, if I attempt the same with the hook, I get the
following error:

check-inherited.rb:9:in initialize': wrong # of arguments(0 for 1) (ArgumentError) from check-inherited.rb:9:in new’
from check-inherited.rb:9:in register' from check-inherited.rb:5:in inherited’
from check-inherited.rb:20

check-inherited.rb

class Base
@@childitems = {}

def self.inherited(subclass)

self.register(subclass)

end

def self.register(subclass)
item = subclass.new
@@childitems[item.name] = item
end

attr_reader :name

def initialize(name)
@name = name
end
end

class Sub1 < Base
def initialize
super(‘child_sub1’)
end
end

not called when testing with self.inherited commented-in

Base.register(Sub1)

end of file

3

Thanks, I suppose the fix is to delay instantiation of the child classes
until some later time.

···

On Thu, Aug 08, 2002 at 05:05:09AM +0900, GOTO Kentaro wrote:

Class#inherited would be called when the line “class Sub1 < Base” is
evaluated. In the time, Base#initialize is not defined yet and the
arity (i.e. # of args) of Sub1.new is 1, which is same to Base.new’s
because the arity of Base#initialize is 1.

–
Alan Chen
Digikata LLC
http://digikata.com