manufacturing methods

[Matthew Pounsett]

Hi there.

Apologies if this is covered somewhere... all the googling I've done on =
the subject has wound up with info on class-factories and and using =
variables in methods. Not exactly what I'm looking for.

The question I've got is related to manufacturing methods. In my =
particular case, I'm using a module that relies heavily on callback =
methods. I need to define a couple dozen callbacks which I'd like to =
all behave in basically the same way. In order to keep my code simple, =
I thought I'd try manufacturing them all from the same basic code.. but =
haven't found a syntax that works.

Though this syntax clearly doesn't work, an example of the sort of thing =
I'm looking for might look like this, assuming I want to create the =
methods "on_foo", "on_bar", and "on_baz":

%w( foo bar baz ).each do |callback|
def on_#{callback}
# callback work here
end
end

Is what I'm attempting to do even possible?

Thanks,
Matt

 

[Josh Cheek]

[Note: parts of this message were removed to make it a legal post.]

Hi there.

Apologies if this is covered somewhere... all the googling I've done on the
subject has wound up with info on class-factories and and using variables in
methods. Not exactly what I'm looking for.

The question I've got is related to manufacturing methods. In my
particular case, I'm using a module that relies heavily on callback methods.
I need to define a couple dozen callbacks which I'd like to all behave in
basically the same way. In order to keep my code simple, I thought I'd try
manufacturing them all from the same basic code.. but haven't found a syntax
that works.

Though this syntax clearly doesn't work, an example of the sort of thing
I'm looking for might look like this, assuming I want to create the methods
"on_foo", "on_bar", and "on_baz":

%w( foo bar baz ).each do |callback|
def on_#{callback}
# callback work here
end
end

Is what I'm attempting to do even possible?

Thanks,
Matt

If you are in a class, you should can do:

class Test
%w( foo bar baz ).each do |callback|
define_method "on_#{callback}" do |param|
puts "This is method #{callback}"
puts "I have received the parameter: #{param}"
puts
end
end
end


test = Test.new
(test.methods - Object.methods).each_with_index do |method,index|
test.send method , index
end



Here is a list of useful methods like this
http://weare.buildingsky.net/2009/08/25/rubys-metaprogramming-toolbox

They are a bit cumbersome to use, though. For example, I don't know how to
set it up to receive a block, and you can't use them certain places.

 

[Robert Klemme]

If you are in a class, you should can do:

class Test
=A0%w( foo bar baz ).each do |callback|
=A0 =A0define_method "on_#{callback}" do |param|
=A0 =A0 =A0puts "This is method #{callback}"
=A0 =A0 =A0puts "I have received the parameter: #{param}"
=A0 =A0 =A0puts
=A0 =A0end
=A0end
end


test =3D Test.new
(test.methods - Object.methods).each_with_index do |method,index|
=A0test.send method , index
end

In this case there is a much simpler solution which does not need
metaprogramming:

class X
def on_event_impl(*a)
printf "args=3D%p\n", a
end

alias foo on_event_impl
alias bar on_event_impl
alias baz on_event_impl
end

If you want to use a bit of metaprogramming in order to not repeat you can =
do:

class Y
def on_event_impl(*a)
printf "args=3D%p\n", a
end

%w{foo bar baz}.each {|m| alias_method m, n_event_impl}
end

Yet another option is to use #method_missing

class Z
def method_missing(s, *a, &b)
if /\Aon_/ =3D~ s.to_s
printf "args=3D%p\n", a
else
super
end
end
end

Kind regards

robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

 

[Matthew Pounsett]

Thanks very much Robert and Josh for your suggestions. It looks like =
all of these work for what I need, so I'll just need to pick one.

Thanks!
Matt