Re: Passing values between procedures(without actually passing them)
Date: Sun, 31 Jan 2010 03:06:24 +1100
Galen Boyer <galen_boyer_at_yahoo.com> writes:
> Tim X <timx_at_nospam.dev.null> writes:
>> LPF <eng.lpsff_at_gmail.com> writes:
>>> It's possible to achieve something like this?
>>> Procedure1(param1,param2) IS
>>> end Procedure1;
>>> Procedure2 IS
>>> --Know the parameters values of Procedure1 at this point(with
>>> dbms_debug, dbms_trace, some V$, ....)
>>> end Procedure2;
>>> The point to this is that i have a lot of procedures(like Procedure1)
>>> calling a Procedure(Procedure2).
>>> So if this could be achieved, i only have to use a simple line like
>>> "Procedure2;" to all procedures(and with the advantage of not being
>>> dependent of the number of parameteres, so future changes wouldn't
>>> affect the Procedure2 call).
>> DO NOT DO IT!
>> this is such a bad idea on so many levels, I can't even begin to list
>> them all. I also doubt it will work technically and even if it did, you
>> are likely to be in all sorts of mess when the oracle version changes.
>> essentialy, you may as well code your whole thing as one huge procedure
>> because doing it how you suggest would be about the same. You would lose
>> all the benefits of scoping, would rely on side effects, would run itno
>> all sorts of type issues, would cripple system efficiency and wuld
>> create a monster that cannot be maintained or easily tested.
>> Programmers should be lazy, but not that lazy. Use decent tools and
>> the changes your talking about are not a problem. In fact, they are a
>> benefit as you can make changes and easily identify and test what has
>> been modified and you only need to understand the bit of code your
>> changing, not the whole system with its hidden side effects.
> Its just the OO world dude. Instead of calling methods with parameters,
> you instantiate objects, set their instance variables and then have the
> object operate.
Well, I guess that is one interpretation of OO! However, that wasn't what the OP asked about, nor was his example referencing an Oracle object definition. While I agree you could possibly reduce the number of calls which pass parameters, OO will not eliminate them. The OPs reference to dbms_debug, trace etc makes it pretty clear that wasn't what he was thinking either.
I don't agree that OO is about procedures without arguments. In fact, every OO language I can think of has methods/procedures/messages which support parameters. The original OO language, smalltalk, used a message passing paradigm. You created an object and then you would send messages to it. those messages might be very simple and might result in the object doing something or possibly doing nothing. this is like calling a method without parameters. However, its vary rare you can do much with objects without passing them new stuff to operate on - without that, they are really just a 'one trick pony'. Most of the methods you will define for an object will take parameters. In smalltalk, where everything is an object, you have things like
5 + 1
where 5 is an object, '+' is a message (procedure/method) and 1 is an arguement/parameter. In java, you see 'setters' all over the place. If you look at the basic Java API, you will see most mehtods take parameters. Likewise, C++ uses parameters all over the place. In fact, in an OO design, you will often have objects like iterators that take collection objects and then operate on them - the collection object is passed as parameter (usually in the constructor).
> Oracle's object oriented features are superb, and I'm not talking about
> just using object types, I'm talking about using OO. At the end of the
> day, its all still SQL and PLSQL.
I agree at the end of the day its all SQL and PL/SQL. However, as someone who has used some really good and some really awful OO languages, I'm afraid Oracle's attempt is not what I would call a superb example. If you want to see a really clear, concise and clean OO implementation, look at smalltalk. If you want to see a really horrible version, check out C++. Java, lies in the middle somewhere and if you want to see a really powerful OO paradigm, then check out CLOS (Common Lisp Object System).
I found Oracles OO stuff to be somewhere between Java and C++. It has some inconsistencies in how things are treated, especially with respect to types. For example, its ability to handle object types depends on whether the object was defined at the SQL or the PLSQL level and it can't handle %TYPE parameters in method definitions (I'm referring to Oracle's object types with methods as opposed to the common object type consisting of just object variables)
The main weakness IMO with Oracle's OO stuff is that it is obviously an after thought - something added to the language to hopefully provide Oracle sales with another compliance buzzword.
for me, the only thing it appears to have added is constructors and inheritance. to a large extent, we already had OO with PL/SQL package Maybe this is what you were referring to when you referred to 'not just the object types'? If so, I would agree. PL/SQL packages have provided all the most useful properties of the OO paradigm, with the exception on inheritance. You have encapsulation, polymorphism/overloading of functins/procedures, instance variables, private/public and even a form of constructor with init blocks. It is even debatable that not having inheritance in packages is a loss - inheritance is sometimes very useful, but it is also probably the most misused/abused feature of OO (with the possible exception of operator overloading in C++!). The only thing that would be worse would be multiple inheritance!
I've used Oracle's OO types with method and constructors stuff a bit and have found it useful for certain cases. For example, I used some of the facilities in a 'proof of concept' test harness that I came across called 'PLUTO'. The work done by the authors was quite interesting, but the implemeentation had a few problems. I've extended it and have been using it as the basis for experimenting with a simple test harness for PL/SQL. The ideas developed by the original authors (whose names escape me just now - I think the code was on googlecode) are interesting and show quite imaginative original application of PLSQL. I don't know yet whether it will amount to anything relly useful, but its an interesting diversion from less inspiring stuff and it gave me an excuse to play with oracle's 'full' object definitions.
If the OP wants to apply OO paradigms to his design, then I would say go for it. Personally, I don't think OO is always the right way to go, but it certainly has been the popular choice over the last decade and there is bound to be lots of people who will udnerstand such a paradigm and provide assistance when/if required. . However, I think it wold be a mistake to adopt that paradigm just so that you can avoid using parameters in procedures. Even inside objects, you don't really want all variables to be instance or class variables - sometimes you want values to be short term or have limited lexical scope. The reduction of calls with parameters comes at a cost - you have to design your application from an OO perspective and have to be confident that adopting that paradigm really does improve upon what you are doing. A badly designed OO system is likely to be a lot worse than a reasonably designed procedural model. I've also found that most OO approaches also add a considerable amount of coding overhead. java is probably the best example of this. While this may not be an issue on a really large project, it can be a problem or difficult to justify in something not so large.
-- tcross (at) rapttech dot com dot auReceived on Sat Jan 30 2010 - 10:06:24 CST