method_added/define_method infinite loop

[Trans]

What's the best way to avoid the classic method_added/define_method
infinite loop?

class X
def self.method_added(name)
p name
define_method(name)
# do something else
end
end

def foo; end
end

This will, of course, print "foo" forever.

As an aside, anyone else think method_added should also receive a
block of the method definition? E.g. this would be a "push" (less the
infinite loop issue):

def self.method_added(name, &block)
define_method(name, &block)
end

Thanks!
T.

 

[ara.t.howard]

What's the best way to avoid the classic method_added/define_method
infinite loop?

class X
def self.method_added(name)
p name
define_method(name)
# do something else
end
end

def foo; end
end

This will, of course, print "foo" forever.

As an aside, anyone else think method_added should also receive a
block of the method definition? E.g. this would be a "push" (less the
infinite loop issue):

def self.method_added(name, &block)
define_method(name, &block)
end

Thanks!
T.

cfp:~ > cat a.rb
class X
class << self
def ignoring_added_methods
ignoring_added_methods = @ignoring_added_methods
@ignoring_added_methods = true
yield
ensure
@ignoring_added_methods = ignoring_added_methods
end

def ignoring_added_methods?
defined? @ignoring_added_methods and @ignoring_added_methods
end

def method_added name
return if ignoring_added_methods?
ignoring_added_methods do
p name
define_methodbar){}
end
end
end

def foo
end
end



cfp:~ > ruby a.rb
:foo


a @ http://codeforpeople.com/

 

[Trans]

cfp:~ > cat a.rb
class X
class << self
def ignoring_added_methods
ignoring_added_methods = @ignoring_added_methods
@ignoring_added_methods = true
yield
ensure
@ignoring_added_methods = ignoring_added_methods
end

def ignoring_added_methods?
defined? @ignoring_added_methods and @ignoring_added_methods
end

def method_added name
return if ignoring_added_methods?
ignoring_added_methods do
p name
define_methodbar){}
end
end
end

def foo
end
end

cfp:~ > ruby a.rb
:foo

nice. i like the way you did that. thanks ara.

only question i have is about thread safety --could the instance var
pose a potential problem with that?

T.

 

[Phrogz]

def ignoring_added_methods?
defined? @ignoring_added_methods and @ignoring_added_methods
end

What was your motivation for the above code instead of simply
def ignoring_added_methods?
@ignoring_added_methods
end

 

[Chris Carter]

This will, of course, print "foo" forever.

As an aside, anyone else think method_added should also receive a
block of the method definition? E.g. this would be a "push" (less the
infinite loop issue):

def self.method_added(name, &block)
define_method(name, &block)
end

I might be missing something, but I cannot think of a practical use
for that. It re-defined the method with the same name and
content....Why?

 

[ara.t.howard]

What was your motivation for the above code instead of simply
def ignoring_added_methods?
@ignoring_added_methods
end

cfp:~ > ruby -d -e ' def foo() defined? @foo and @foo end; foo() '


cfp:~ > ruby -d -e ' def foo() @foo end; foo() '
-e:1: warning: instance variable @foo not initialized


been trying to get the habit... it's tough! ;-)

cheers.

a @ http://codeforpeople.com/

 

[ara.t.howard]

only question i have is about thread safety --could the instance var
pose a potential problem with that?

probably. maybe (untested):

cfp:~ > cat a.rb
class X
class << self
def ignoring_added_methods
ignoring_added_methods = @ignoring_added_methods
@ignoring_added_methods = true
yield
ensure
@ignoring_added_methods = ignoring_added_methods
end

def ignoring_added_methods?
defined? @ignoring_added_methods and @ignoring_added_methods
end

def method_added name
Thread.critical = true
return if ignoring_added_methods?
ignoring_added_methods do
p name
define_methodbar){}
end
ensure
Thread.critical = false
end
end

def foo
end
end

cheers.


a @ http://codeforpeople.com/

 

[Trans]

I might be missing something, but I cannot think of a practical use
for that. It re-defined the method with the same name and
content....Why?

I'm impractical ?

meta-programming. In this instance, I was working on a Traits idea. I
need to rename every method defined and keep track of it and replace
it with a method that weaves together these renamed methods.

T.