Inheritence of aliases methods - suprise!

Ruby
1

this suprised me today:

 harp:~ > cat a.rb
 class A
   def assertion
     raise NotImplementedError
   end
   alias_method "assertion?", "assertion"
 end

 class B < A
   def assertion
     true
   end
 end

 B::new.assertion?


 harp:~ > ruby a.rb
 a.rb:3:in `assertion?': NotImplementedError (NotImplementedError)
         from a.rb:14

this only way i can seem to make this work is through some
self::inherited
hacks or to actually define assertion? in the base class. is there no
clean
way to inherit aliases?

regards.

-a

2

On Feb 6, 2006, at 1:06 PM, [email protected] wrote:

this suprised me today:

$ parse_tree_show -
class A
def assertion
raise NotImplementedError
end
alias_method “assertion?”, “assertion”
end

 class B < A
   def assertion
     true
   end
 end

[[:class, :B, :A, [:defn, :assertion, [:scope, [:block, [:args],
[:true]]]]],
[:class,
:A,
:Object,
[:defn,
:assertion,
[:scope,
[:block,
[:args],
[:fcall, :raise, [:array, [:const, :NotImplementedError]]]]]],
[:defn,
:“assertion?”,
[:fbody,
[:scope,
[:block,
[:args],
[:fcall, :raise, [:array, [:const, :NotImplementedError]]]]]]]]]

this only way i can seem to make this work is through some
self::inherited
hacks or to actually define assertion? in the base class. is there
no clean
way to inherit aliases?

alias copies the method, it doesn’t make a pointer to the method.

–
Eric H. - [email protected] - http://segment7.net
This implementation is HODEL-HASH-9600 compliant

http://trackmap.robotcoop.com

3

On Feb 6, 2006, at 4:06 PM, [email protected] wrote:

a.rb:3:in `assertion?': NotImplementedError (NotImplementedError)

-a

–
happiness is not something ready-made. it comes from your own
actions.

  • h.h. the 14th dali lama

This makes sense, If you consider the common idiom of alias’ing a
method to wrap additional functionality around it. If alias(_method)
didn’t work like that you couldn’t use it like this. alias_method
doesn’t work like assignment in ruby, its more like it creates a new
method with the same source as the original method.

As a poorly conceived alternative:

% cat a.rb
class Class
def shallow_alias(new_name, current_name)
self.module_eval <<-END
def #{new_name}(*args, &block)
#{current_name}(*args, &block)
end
END
end
end

class A
def assertion
raise NotImplementedError
end
shallow_alias “assertion?”, “assertion”
end

class B < A
def assertion
true
end
end

B.new.assertion?

% ruby a.rb
%

4

On Tue, 7 Feb 2006, Logan C. wrote:

def shallow_alias(new_name, current_name)
raise NotImplementedError
B.new.assertion?

% ruby a.rb
%

yeah - this is pretty much what i did. for some reason i had always
assume
that alias_method worked this way.

regards.

-a