in reply to Eliminating conditional code for GUI and text-mode operation

This is a concern as I am considering an incremental move over to a OO style and higher levels of abstraction. How might OO design or some other abstraction help me support this dual-interface ability?

Easily 

{
   package UI;
   ...
   sub refresh_track_display {}
   ...
}

{
   package UI::Graphical;
   our @ISA = 'UI';
   ...
   sub refresh_track_display {
      ...
   }
   ...
}

{
   package UI::Text;
   our @ISA = 'UI';
   ...
   # Inherit no-op refresh_track_display.
   ...
}

...
$ui->refresh_track_display();
...

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Re^2: Eliminating conditional code for GUI and text-mode operation
by gnosti (Chaplain) on Dec 07, 2007 at 09:50 UTC
    This is good, because I have a few more of these conditionals, and everywhere around them feels brittle and I feel pinched by them. These are thorns I can remove from my dreams as well. :-)

    I am happy that I can refine code that I already have. I think I'm no longer envious of those LISP guys, living in their clouds of parentheses.

    For the first time, I feel that I understand how a hierarchy would work, and in fact, have used them already with Tk.

    A UI class might be at the top, a Session might inherit from that, and specify a group of recordings and data structures expressing the routing and processing specifics(as it already does in my procedural code).

    I can see how each level can add its own subroutines in a neat way. I am gleeful that I can accomplish this directly using something lightweight like Object::Tiny. Encouraged by the simplicity, excited to get at these possibilities with less boilerplate, from which I would also like to liberate my dreams and waking hours.:-)

    I am happy to think I can develop more succinct ways to say and get to what I want in code.

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Re^2: Eliminating conditional code for GUI and text-mode operation
by gnosti (Chaplain) on Dec 08, 2007 at 09:09 UTC
    I'm thrilled to begin getting this... although some hours are going by...

    As stand-alone code, this example produces the expected output. As a module (built with the h2xs boilerplate) make test fails with:

    Tried to use 'TestOO'. # Error: Can't locate object method "new" via package "UI::Graphical" at /media/jroth/ecmd-dev/TestOO/blib/lib/TestOO.pm line 56.

    Any ideas about this? I just pasted this stuff into the 'precompiled methods go here' indicator in the boilerplate.

    Is there a reason why the children would inherit 'new' from the superclass in one context and not in another? 

    package UI;
use Object::Tiny qw(dummy);
sub hello {print "superclass hello\n"};

package UI::Graphical;
@ISA = 'UI';
sub hello {print "make a window\n";}

my $ui = UI->new;
$ui->hello;
$ui = UI::Graphical->new;
$ui->hello;
1;

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[d/l]
      Are you sure that's the code you ran? It should work. And it works for me. 
      >perl 655812.pl
superclass hello
make a window

      [download]

      use Object::Tiny qw(dummy);
      can be written as
      use Object::Tiny;
      but not as
      use Object::Tiny qw( ); or
      use Object::Tiny ( );
      You would get the error you showed if you did one of the latter two.

      Also, if you have no members, you can use
      $ui = 'UI'; instead of $ui = UI->new();, and
      $ui = 'UI::Graphical'; instead of $ui = UI::Graphical->new();.
      However, you'll probably need some members, so you might as well continue the way you are going.

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