Rails - Jul 2005 - Wrapping methods in derivative classes with logic from the super class

Hello,

I have a super class called TaskManager, a TaskManager is a separate 
ruby process which I fork. I have various derivative classes which 
follow this pattern.

For accounting purposes I need to know which of these processes
is running and which is not. TaskManager is a decendant of 
ActiveRecord::Base so I''m keeping track by modifying a field in
the table.

I can do this in each derivative like this:

class FooManager < TaskManager
  def run
    self.running = 1
    self.save
    begin
      # FooManager procedure
    ensure
      self.running = 0
      self.save
    end
  end
end

What I would like to know is if there is some way I can ''wrap''
the
run method in the derivative classes so instead my FooManager class 
would simply be:

class FooManager < TaskManager
  def run
    # FooManager procedure
  end
end

The begin ... ensure ... end would be defined in the super class.

Is there a way I can achieve this?

Thanks,
-- 
Dominic Marks

On Sunday 17 July 2005 19:44, Dominic Marks wrote:
> Hello,
>
> I have a super class called TaskManager, a TaskManager is a separate
> ruby process which I fork. I have various derivative classes which
> follow this pattern.
>
> For accounting purposes I need to know which of these processes
> is running and which is not. TaskManager is a decendant of
> ActiveRecord::Base so I''m keeping track by modifying a field in
> the table.
>
> I can do this in each derivative like this:
>
> class FooManager < TaskManager
>   def run
>     self.running = 1
>     self.save
>     begin
>       # FooManager procedure
>     ensure
>       self.running = 0
>       self.save
>     end
>   end
> end
>
> What I would like to know is if there is some way I can
''wrap'' the
> run method in the derivative classes so instead my FooManager class
> would simply be:
>
> class FooManager < TaskManager
>   def run
>     # FooManager procedure
>   end
> end
>
> The begin ... ensure ... end would be defined in the super class.
>
> Is there a way I can achieve this?
I figured out how I am going to approach this for now. Since I call
the run method from my own code, and it will not be called from anywhere
else, I can simply write an additional method in TaskManager to do
my bidding and then call the run method in the derivative class. So
long as none of the decendants interfere with this method, and no code
calls the run method directly this meets all my goals.

If anyone has a better reccomendation I''d still like to hear it though.
> Thanks,
Cheers,
-- 
Dominic Marks

Hi,

I''d like to write my own method to extend the Time class. My problem is
where to put the file once I''m done. Is there any directory where I can
put it that will make it automatically available to my whole
application, or will I always have to "require" it in each separate
file? Thanks.

Alison Rowland

On Monday 18 July 2005 01:03, Alison Rowland wrote:
> I''d like to write my own method to extend the Time class. My
problem
> is where to put the file once I''m done. Is there any directory
where
> I can put it that will make it automatically available to my whole
> application, or will I always have to "require" it in each
separate
> file? Thanks.
You can put the file in the lib directory and require it at the end of 
config/environment.rb

Michael

-- 
Michael Schuerig                  Airtight arguments have
mailto:michael-q5aiKMLteq4b1SvskN2V4Q@public.gmane.org        vacuous
conclusions.
http://www.schuerig.de/michael/   --A.O. Rorty, Explaining Emotions

Hello Dominic !

Dominic Marks said the following on 2005-07-17 17:29:
> On Sunday 17 July 2005 19:44, Dominic Marks wrote:
> I figured out how I am going to approach this for now. Since I call
> the run method from my own code, and it will not be called from anywhere
> else, I can simply write an additional method in TaskManager to do
> my bidding and then call the run method in the derivative class. So
> long as none of the decendants interfere with this method, and no code
> calls the run method directly this meets all my goals.
What you have described above is the Template Method pattern[1].  If you 
have never read the Design Patterns book[2], check it out.

Bye !
François

[1] http://c2.com/cgi/wiki?TemplateMethodPattern
[2] http://c2.com/cgi/wiki?DesignPatternsBook