[Tutor] impact of OO

[alan.gauld@bt.com]

> I have a general question about Object Oriented programming 
> in general:  why is it so lauded by... well, by everyone?

Its not. There are several minority groups who believe that 
OO is a retrograde step. Others believe that things like 
Functional Programming are more important etc etc. But 
the general opinion is that OO is a big improvement on 
traditional "Structured Methods"


There are lots of reasons, most only relevant to large 
projects so its hard for the newbie writing programs of 
only a few hundred lines to see the avantages. But one 
your prohgrams get into the tens of thousands of lines 
the benefits become far more obvious. However...

> to with a group of variable names.  It's hard to describe, but this 
> makes it much easier -- 

... even in smaller projects it can show benefits in ease 
of comprehension - as you've seen.

> but it is far more organized and cleaner.

We used to have one maintenance programmer looking after, 
on average 20,000 lines of code(in C) when we moved to 
OO designs we have one programmer looking after 100,000 
lines. A 5 to 1 improvement, mainly due to the better 
cohesion of the designs using OOP.

> ...but I still don't really see how 
> it's that big a deal -- it's simply a different way of 
> organizing code, as far as I can tell.

Which is the hardest aspect of industrial grade 
software engineering. Organizing code such that when one 
bit changes you don't need to change everything elsder 
with it has been the biggest headache in softwae since 
the start of commercial programming. OOP helps do just that.

> Please prove me wrong and help me see how OO "changed everything".

It doesn't change everything but it helps a lot.

There are other aspects to OOP too that we haven't 
touched on. The ease of extending existing code without 
changing it (and thus breaking existing code relying 
on the bit being extended) via inheritance. The way 
OOP eliminates long if/elif/else chains (or switch 
statements)via polymorphism (see the OOP page in my 
tutor for a discussion of polymorphism and inheritance)

The ability to build whoile abstract frameworks which 
act as application templates. These can quickly be 
added to to produce new apps - most GUI frameworks 
are done this way.


> PS:  Also, I have heard someone say that "in Java everything is an 
> object".  

Its a lie. In Java everything is in a class... 
only some things are objects. There is a big difference 
which the Java community seems to disregard. But claiming 
that everything is anobject is a big marketing coup!


> Java, especially since there are many employers 

This sadly is true. Mainly a result of the "emperors new clothes" syndrome
but none the less Java is taking over.


in my area (Boston) 
> advertising an interest in Java programmers (and I will be 
> out of a job 
> as soon as my project is finished).  Sadly, much more than Python or 
> PHP.  But it seems like a big language to learn.
> 
> 
> 
> 
> 
>