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comp.lang.ruby

Inspetting a method's caller

Alberto Santini

3/19/2008 12:54:00 PM

Hello.
How can i know a function's caller method? E.g.

class A
def do_stg(n)
b = B.new
b.do_xyz(n)
end
end

class B
def do_xyz(n)
# -> Here i want to know that
# -> This method has been called
# -> From A#do_stg
n + 1
end
end

Kernel#caller does not help.. i don't care what file or line a function
has been called, and i couldn't find nothing helpful on ruby-doc nor by
searching google :|
Please keep in mind i'd like to know that do_xyz has been called by
do_stg -> WHICH IS A METHOD OF THE "A" CLASS <-

Thanks for your help :)
--
Posted via http://www.ruby-....
5 Answers

mt

3/19/2008 1:32:00 PM

0

I've always seen that whenever you need something like this, there's
always a better design choice that you can make. Like what would you
do in languages that didn't have caller etc etc.

Its still a hack, (because ideally you shouldn't be needing this IMO),
but you can make the caller send in an extra argument, putting its
description/ID/Name there.

MT

On Wed, Mar 19, 2008 at 8:53 PM, Alberto Santini
<santini.alberto@gmail.com> wrote:
> Hello.
> How can i know a function's caller method? E.g.
>
> class A
> def do_stg(n)
> b = B.new
> b.do_xyz(n)
> end
> end
>
> class B
> def do_xyz(n)
> # -> Here i want to know that
> # -> This method has been called
> # -> From A#do_stg
> n + 1
> end
> end
>
> Kernel#caller does not help.. i don't care what file or line a function
> has been called, and i couldn't find nothing helpful on ruby-doc nor by
> searching google :|
> Please keep in mind i'd like to know that do_xyz has been called by
> do_stg -> WHICH IS A METHOD OF THE "A" CLASS <-
>
> Thanks for your help :)
> --
> Posted via http://www.ruby-....
>
>

Alberto Santini

3/19/2008 2:11:00 PM

0

> but you can make the caller send in an extra argument, putting its
> description/ID/Name there.

Of course i can, i just *don't want* to do this. For example, imagine i
want to access a database table that (by -> convention <-) has the same
name of a class. Imagine i have a DBHelper class that contains a
DBHelper#find method used to find records on the database. if
DBHelper#find is called from a Ball object i want to lookup on the
"ball" table, it it's called from a Cube object i want to search the
"cube" table, etc. This is just the simplest usage that came to my mind,
but i guess there are hundreds. Obviously, i can implement DBHelper#find
in a way like this:

def find(table_name = "", criteria = {})
...
end

and call it like this:

find(self.class.to_s, {:id => 5})

It is just *not what i want to do*.

So, coming back to my question, is there a simple way to get the wanted
class name, without haveing to parse Kernel#caller?

Thanks.
--
Posted via http://www.ruby-....

Ben Oakes

3/19/2008 2:35:00 PM

0

On Wed, Mar 19, 2008 at 9:10 AM, Alberto Santini
<santini.alberto@gmail.com> wrote:
> > but you can make the caller send in an extra argument, putting its
> > description/ID/Name there.
>
> Of course i can, i just *don't want* to do this. For example, imagine i
> want to access a database table that (by -> convention <-) has the same
> name of a class. Imagine i have a DBHelper class that contains a
> DBHelper#find method used to find records on the database. if
> DBHelper#find is called from a Ball object i want to lookup on the
> "ball" table, it it's called from a Cube object i want to search the
> "cube" table, etc. This is just the simplest usage that came to my mind,
> but i guess there are hundreds. Obviously, i can implement DBHelper#find
> in a way like this:
>
> def find(table_name = "", criteria = {})
> ...
> end
>
> and call it like this:
>
> find(self.class.to_s, {:id => 5})
>
> It is just *not what i want to do*.
>
> So, coming back to my question, is there a simple way to get the wanted
> class name, without haveing to parse Kernel#caller?
>
> Thanks.
> --
>
>
> Posted via http://www.ruby-....
>
>

There's something in Ruby Facets that seems related: Binding#called

http://facets.rubyforge.org/quick/rdoc/core/classes/Binding.ht...

I've only ever used it when I'm working with trace statements when a
debugger isn't available or doing the job I need it to.

-- Ben

mt

3/19/2008 3:04:00 PM

0

:)

I don't know, but maybe you can implement the methods you *want* as a
module method, and use them in your classes that you need such
functionality built-into, which would ensure they'll be able to know
which class they're under whenever they're called.
like

module M
def foo
puts self.class
end
end

class A
include M
end

class B
include M
end

a= A.new
a.foo => A
b= B.new
b.foo => B

I might be completely off base here, but i'll still *try* to give you
a design based resolution, more often than not, that causes less
problems in the long run.

HTH
Mt.

Alex Fenton

3/19/2008 4:31:00 PM

0

Alberto Santini wrote:
>> but you can make the caller send in an extra argument, putting its
>> description/ID/Name there.
>
> Of course i can, i just *don't want* to do this. For example, imagine i
> want to access a database table that (by -> convention <-) has the same
> name of a class. Imagine i have a DBHelper class that contains a
> DBHelper#find method used to find records on the database. if
> DBHelper#find is called from a Ball object i want to lookup on the
> "ball" table, it it's called from a Cube object i want to search the
> "cube" table, etc.

Perhaps your DBHelper class would be better designed as a module that is
included in the Ball/Cube.etc classes, or extends its instances?

alex