rewriting method_missing

[Tyler Pirtle]

I'm not even sure if this would be possible but I think I need some
help. In the spirit of the method_missing hall of fame, I want to be
able to do..sort of a nested method_missing.

how can i get at
Instance.bogus_member1.bogus_member2

bogus_member2 through the class of Instance?
Or better yet, suppose bogus_member1 returned an object, how could I
get at bogus_member2 through the class of the object of bogus_member1?

I've tried just using method_missing statements in 2 different
classes, but Ruby seems to want to perform the last method first - and
because bogus_member1 doesn't exist its trying to call something from
NilClass.

Ideally, what will happen is that bogus_member1 will be an object that
will be instantiated based on its own criteria - for example, suppose
every day of school you had a new teacher

School.MrSmith.homework
but the next day
School.MrsJones.homework

MrSmith & MrsJones are objects that get instantiated as Teachers based
on their criteria -

class School
def method_missing(*args)
...
Teachers.new(args[0])
end

What i'd like to do is at that same line...

Teacher.new(args[0]).send(args[1..-1]))

But it seems as if Ruby is going in the other direction.(end to start)

What can I do?

 

[David A. Black]

Hi --

I'm not even sure if this would be possible but I think I need some
help. In the spirit of the method_missing hall of fame, I want to be
able to do..sort of a nested method_missing.

how can i get at
Instance.bogus_member1.bogus_member2

bogus_member2 through the class of Instance?
Or better yet, suppose bogus_member1 returned an object, how could I
get at bogus_member2 through the class of the object of bogus_member1?

I've tried just using method_missing statements in 2 different
classes, but Ruby seems to want to perform the last method first - and
because bogus_member1 doesn't exist its trying to call something from
NilClass.

Ruby goes from left to right, so you'll get the nil message if
Instance is returning nil, or if Instance.bogus_member1 is returning
nil.

Ideally, what will happen is that bogus_member1 will be an object that
will be instantiated based on its own criteria - for example, suppose
every day of school you had a new teacher

School.MrSmith.homework
but the next day
School.MrsJones.homework

MrSmith & MrsJones are objects that get instantiated as Teachers based
on their criteria -

class School
def method_missing(*args)
...
Teachers.new(args[0])
end

What i'd like to do is at that same line...

Teacher.new(args[0]).send(args[1..-1]))

But it seems as if Ruby is going in the other direction.(end to start)

I'm not clear on what the criteria or args are. What exactly are you
trying to send to the new Teacher object?

What can I do?

I don't know if this will help, but here's some playing around with
this:

class Teacher
attr_accessor :name
def initialize(name)
self.name = name
end

def homework
"This is an assignment from #{name}..."
end
end

class School
class << self
def method_missing(*args)
Teacher.new(args[0])
end
end
end

puts School.MrSmith.homework
puts School.MrsJones.homework

Output:

This is an assignment from MrSmith...
This is an assignment from MrsJones...

I don't know that this will scale very well or offer you much
functionality, though. It looks like a case of trying to use
method-call syntax (the dot) for argument semantics (passing objects
to each other), which may be asking too much of the humble dot.


David