Background:

Recently I bought myself "Object Oriented Perl" by the esteemed Damian Conway. Interesting reading I thought, but I know the old saying that reading isn't knowing.

So I thought the the next project would be OO, getting my feet wet and all that.

The Project:

The project is what you might call an order confirmer, that gets information from SQL-databases, generates nice output in MS Word and automatically sends the confirmation to client as either Fax or PDF.

The Problem:

I have done similar, in some sense, imperative program where the data has been organized as a treelike structure in a hash, and where I have showed a reference to this hash around to the various subroutines. This has worked well the main feature being short argument lists, but I imagined that OO would be safer and prettier.

In the non-OO solution I would have something like this

Most of the toplevel keys of the hash maps *almost* to tables in the database, however the real app is much more complicated than the example below suggests, so relying more on the database is not an option.

%obj = (
        CFG => { 
            DSN => 'test',
            PDF => 'MyPDFdriver',
        },
        CLIENT => {
            10101 => {
                Name     =>    'Client Name1',
                Adress     =>    'Adress1',
                Phone     =>     '555-7865',
                Media    =>     'Mail',
            },
            10102 => {
                Name     =>    'Client Name2',
                Adress     =>    'Adress2',
                Phone     =>     '555-7866'
                Media    =>     'Fax',
            },
        },
        ORDER => {
            2ZXWEQ    => {
                CLIENT     => 10101,
                Info    => 'Pix proj 123',
                ITEMS     => [VX12345, VX12346],
            },
            3ZSIUY    =>    {
                CLIENT    => 10101,
                Info     => 'Something else',
                ITEMS     => [VX12347, VX12348],
            },
        },
        ITEM =>    {
            VX12345    => {
                ORDER     => 2ZXWEQ,
                TYPE     => HW33,
                Price    =>    123,
            },
            VX12346        => {
                ORDER     => 2ZXWEQ,
                TYPE     => HW33,
                Price    =>    123,
            },
            VX12347    => {
                ORDER     => 3ZSIUY,
                TYPE     => HW34,
                Price    =>    155,
            },
            VX12348    => {
                ORDER     => 3ZSIUY,
                TYPE     => SW12,
                Price    =>    1203,
            },
        },
        TYPE    => {
            HW33    =>     'foo manipulator',
            HW34    =>    'bar stimulator',
            SW12    =>    'baz simulator',
        },
    );
    


so 

print $obj->{TYPE}{ $obj->{ITEM}{VX12348}{TYPE} }    

would yield 

baz stimulator

[download]

So I figured that making a class of each of the top level hash keys and somehow make it act as a container for instances of that class.

However my limited OO knowledge can't seem to grasp how to get or set the different attributes of a parallell branch in the tree structure for instance.

Should I have organized the data differently ?

Is it altogether a bad case for OO ?

Does anyone have any ideas ?

TIA

In reply to OO or just OOps ? by guha

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