Trying to understand object oriented programming

Hi all,
I'm new to programming and I'm trying to learn C and Objective-C to eventually write an iPhone/iPad app.
I want to make sure I'm understanding some fundamental Object Oriented principles and so I'm starting with a very basic program.
I've produced a class called CartesianPoint which has an x and y variable plus methods to set and return these variables and also a method to calculate the magnitude from the origin.
What I would like to do now is to extend the program to have a CartesianVector class.
I'm a little unsure as to whether a Vector is a subclass of a Point or whether a Point is a subclass of a Vector... or neither?
Secondly, I'm a little unsure of how to implement the vector class to use two point objects. How should the header and implementation files be set up to receive point objects from the main.m program?
I'd like to also try and extend the program to include other ways of defining a vector (i.e. origin, unity vector and magnitude).... and then use the vectors to build 2D shapes.
Many thanks,
Glyn
Message was edited by: GlynC
Message was edited by: GlynC

Hi Glyn -
I agree with William and would vote for "neither". I see a subclass as a specialization of its superclass, not, for example, something contained by its superclass. A container relationship might apply to a subview and its superview, yet the class of the superview could be a specialization of the subview's class so the subview's class might be the parent of the superview's class. The classic example of cat as a subclass of animal (cat:animal) can be misleading if we see the relationship as member:group. Cat is a subclass of animal because it's a specialization.
Also ask, "What's accomplished by making a subclass"? Does the subclass want to use all or most of the parent's instance variables and methods? Could the job be done any other way? Are any of those ways simpler or do they lead to more reusable code?
One of the best examples (from the Cocoa docs?) is about a programmer who needs a specialized array. A newbie might immediately attempt a subclass of NSArray (a rather tricky subclassing job as it happens). In most cases however, the correct solution would be a class which includes an NSArray* type instance variable.
Hope some of the above is helpful!
\- Ray

Similar Messages

Trying to understand the basic concept of object oriented programming.

I am trying to understand the basic concept of object oriented programming.
Object - a region of storage that define is defined by both state/behavior.
( An object is the actual thing that behavior affects.)
State - Represented by a set of variables and the values they contain.
(Is the location or movement or action that is the goal that the behavior is trying to accomplish.)
Variables- (What does this mean?)
Value - (What does this mean?)
Behavior - Represented by a set of methods and the logic they implement.
( A set of methods that is built up to tell's the how object to change it's state. )
Methods - A procedure that is executed when an object receives a message.
( A very basic comand.For example the method tells the object to move up, another method tells the method to go left. Thus making the object move up/left that combination is the behavior.)
Class - A template from which the objects are created.
( I am very confused on what classes are.)
- The definitions of the words I obtained from the "Osborne Teach Yourself Java". The () statements are how I interperate the Mechanisms (I do not know if Thats what you call them.) interact with each other. I understand my interpretation may be horribly wrong. I will incredibly appreciate all the support I may get from you.
Thank you

Object oriented programming is a replacement for the older idea of procedural programming (you can research procedural programming in google). As I understand it, in procedural programming, you have a step by step set of function calls to accomplish some task. Each function receives a data structure, manipulates it, and passes it to the next function. The problem with this is that each function preforms some action for the overall task and can't easily be reused by some other task. Its also harder to read the flow of what is happening with raw data structures flying all over the place.
In object oriented programming, an object calls a function of another object and receives back, not a data structure, but another object. Objects contain a data structure that can only be accessed by its functions. An object is not so much a sub component of a bigger task, as it is a service that any other task can use for any purpose. Also, when you pass an object to the caller, the caller can ask questions about the data structure via its functions. The developer doesnt have to know what the previous function did to the data by reading up on any documentation, or having to reverse engineer the code.
I suggest the best way of learning this is to code something like a library object.
A library object contains a collection of book objects
A book object contains a collection of chapter objects
A chapter object contains a collection of paragraph objects
A paragraph object contains a collection of sentence objects
A sentence object contains a collection of word objects.
Add functions to each object to provide a service
Example: A library object should have a:
public void addBook(Book book)
public Book getBook(String title)
public boolean isBookInLibrary(String title)
The key is to add functions to provide a service to anyone who uses your object(s)
For example, what functions (service) should a paragraph object provide?
It shouldn't provide a function that tells how many words there are in a sentence. That function belongs to a sentence object.
Lets say you want to add a new chapter to a book. The task is easy to read
if you write your objects well:
Sentence sentence1=new Sentence("It was a dark and stormy night");
Sentence sentence2=new Sentence("Suddenly, a shot ran out");
Paragraph paragraph=new Paragraph();
paragraph.addSentence(sentence1);
paragraph.addSentence(sentence2);
Paragraphs paragraphs=new Paragraphs();
paragraphs.addParagraph(paragraph);
Library library= new Library();
library.getBook("My Novel").addChapter("Chapter 1",paragraphs).
Now, lets say you want to have a word count for the entire book.
The book should ask each chapter how many words it contains.
Each chapter should ask its paragraphs, each paragraph should ask
its sentences. The total of words should ripple up and be tallied at each
stage until it reaches the book. The book can then report the total.
Only the sentence object actually counts words. The other objects just tallies the counts.
Now, where would you assign a librarian? What object(s) and functions would you provide?
If written well, the project is easily extensible.

Join Query in Object Oriented Programming

Hi,
I am trying to understand better how OO programming should work in CFC context. For example, I have two database tables: Customer and Order. So I create two CFCs, one for Customer and another for Order. In the CFCs I have query functions (select, insert, update) to access and manipulate data in the underlying tables.
Now, I need to create a new CFC, OrderReport. This CFC takes in customerID and returns data pulled from both Customer and Order tables. I can just have a join query that pulls data from these two tables. However, I have been wondering whether this method is within the spirit of Object Oriented programming. Should this CFC be able to access directly to the two tables? Or should I pull data separately using Customer CFC and Order CFC, and join them locally (ie. in OrderReport CFC)? This latter method would be a lot slower to run than the first method.
Can you advise me as to what the best practice is in the context of OO programming? Thank you.

This is a common question for those new to OO programming. Here are some of
my thoughts on the topic.
OO programming has nothing to do with tables. Your tables are essentially a
relational storage of one part of a business concept. It just so happens
that most of the data you need to support the business concept of Customer
and the business concept of Order are stored in tables named Customer and
Order. This is because database tables often relate to a business concept. I
think you'd find that to get the entire customer, you'd have to get data
from other tables, like State and Gender and other such tables.
The reason why I bring this up is to begin to separate your thinking.
Databases are concerned with efficient storage and retrieval of data.
Objects (CFCs) are not concerned at all with storage of data. Objects are
concerned with encapsulating business logic relating to a business concept.
Just like your database may have columns not needed by your CFCs, your CFCs
likely have methods not needed by your database.
For example, if you wanted to know, in your application, whether to show an
In Store Pickup option, you may wish to add an isLocal() method to your
customer object. This would ( we'll pretend) get the customer's zip code,
and look it up in GeographicalPostalServiceMapper object to tell us how far
away the customer is.
The point is, the right OO (CFC) design has nothing to do with how your
tables are organized in the database. You would do well to concern yourself
with the needs of the application and what sort of questions you need your
customer object to be able to answer to the other parts of your application.
Like, isLocal(), isOver21(), isBadCreditRisk() and so on.
As to your question about joins, you would do well to use joins in your
application. Do not be afraid of using queries to get the information you
need. Especially for reporting queries. In these cases, I often make an
object called a xxxList. My CustomerList.cfc would have the different ways
to list customer data, like CustomerOrders and CustomerOrderReturns. I'd
hide this join relationship inside of the CustomerList object so only the
CustomerList object has the SQL. That's usually enough encapsulation for the
needs of my application.
Truly, it doesn't matter what the name of the object is, just that you
assign it the responsibility of managing a business concept and keep that
business concept inside that object. You seem to have suggested
CustomerReport.cfc and that would be a fine name for an object that can
return numerous Customer Reports.
Happy Coding
DW

Object oriented programming in LabVIEW

Please send this message to everybody who has an opinion about this.
Please try to keep it short, but if you can't control yourselves, let
it all out!
I would like to have your opinions about the nature of Labview and it's
ability to support object oriented programming.
I have a couple of questions to fire the discussion.
1- Do you think that LV was built to support OO Programming?
2- Is OO the only way we have to support large applications, or is it
feasible to support it with a good dataflow architecture including all
the flowcharts and all the data definitions?
3- Is LV going to stay "dataflow" or is it going to become OO?
4- What would be the great benefits of turning LV to OO that we don't
already have w
ith the dataflow approach?
5- My opinion is that trying to implement OO in LabVIEW, is like trying
to
Thank you all for your time.
Sent via Deja.com
http://www.deja.com/

> 1- Do you think that LV was built to support OO Programming?
LV was initially designed in 1983. OOP existed at that point,
but LV wasn't designed to be OO. It was designed to allow
engineers and researchers a simple language appropriate
for controlling their research labs from a computer.
> 2- Is OO the only way we have to support large applications, or is it
> feasible to support it with a good dataflow architecture including all
> the flowcharts and all the data definitions?
OO lends itself to large projects because it provides
abstraction, encapsulation, and organizes code into
modules that can more easily be implemented independent
of one another since they can be specified in finer
detail. Also, the compilers help to enforce the
specifications providing they can be encoded in the
interface between objects.
These OO principles were already a part of big projects
long before there were OO languages. It was just that
the language didn't necessarily have features which
supported it. Similarly, they can be a part of big
projects today despite the language being used.
LV 2 style globals, which as the name suggests were
in use long ago, encapsulate data with an interface.
They disallow arbitrary access to the data and can be
used to enforce correct access. With other functions
layered on top, you get a nice interface to stored data.
Functions and structs/clusters abstract away details.
Building a subVI that does an FFT means that for 99%
of the uses, you don't need any more information except
that this block performs an abstract mathematical function,
an FFT. The implementation can be completely changed
to speed it up or make it more accurate and your code
isn't affected. Its abstract definition still holds, so
your code still works.
There are other things that OO languages bring to the
table that LV, and GOOP don't yet offer. In my opinion,
a few more OO features can be added to LV to allow for
even larger projects in the future provided they are used
well.
Earlier posts pointed out that C++ doesn't guarantee that
a project will succeed. OO features are just another tool,
and the tool can be misused leading to a failed project.
This is true to LV, C, C++, and all other engineering tools.
The key is using the tools at hand to best solve the
problems we face. Not glorifying or blaming the tools for
the state of the project.
> 3- Is LV going to stay "dataflow" or is it going to become OO?
LV is dataflow to the core. The definition of what data
is flowing may be expanded, but it will still be data
flowing down wires from one node to another that accounts
for how the program executes.
One of the limitations of the current GOOP is that all
objects are dealt with by a reference. By adding
language features, objects could be made to flow down
the wire, just like strings and arrays, meaning that
branching a wire doesn't lead to side-effects,
and there is no need to dispose objects.
> 4- What would be the great benefits of turning LV to OO that we don't
> already have with the dataflow approach?
Remember when LV didn't have typedefs? It was easy for
a cluster datatype to change once a project was underway.
That usually led to lots of edits on other panels to get
them back in synch. Without the unbundle by name, you
then went through the diagrams fixing all of the bundlers
and unbundlers to have the right number of terminals.
Changing the order of the cluster was even worse since
the diagrams may not bread, they might just access the
wrong field instead.
In many respects, an object is just another step along the
same path. An object is a typedef that can have code
associated with it for access -- maybe like Array and
Cluster Tools. Some of the typedef contents might be
publicly accessable, like now, while other elements are
hidden, only available to the implementation of the
typedef. That would force the user to use your functions
to manipulate things rather than hacking away at the
typedef contents. As an example, a LV string is really
just a cluster of size and characters. Since the diagram
can only modify the string using the string functions, you
never get the size and characters out of synch. That is
until you take it into LV generated code, a DLL or CIN
where you have access to the inner fields.
A related problem is that current typedefs are transparent
to built-in LV functions. If your typedef is just some
numbers, LV will be happy to perform arithmetic on your
typedef. Maybe this is what you want, but if this doesn't
make sense on your typedef, then your left with adding a
Boolean or a string so that the arithmetic isn't allowed.
Ideally, you would be able to state that = makes sense, >
and < don't, + and - only operates on the first numeric, and
* is something that you implement yourself. There would be
some safeguards so that the user of your typedef, which
includes you, wouldn't accidentally mangle the typedef
contents.
These may not seem like much at first, but they allow for
much more abstraction and better encapsulation. Finally,
there is a technique called inheritance that allows for
similar objects to be acted on by common code in one
location, and by specific code in another location depending
on which type of object is actually there at runtime.
This of usually done today by switching out on some inner
tag and dealing with each type in its own diagram. This
works fine until projects get large and teams get large.
Inheritance is a different way of implementing the exact
same thing that usually works much better for bigger teams
and bigger projects.
> 5- My opinion is that trying to implement OO in LabVIEW, is like trying
> to
Is this a fill-in-the blank question? It is difficult today
because the LV language doesn't yet support OO very well.
Early C++ was implemented on top of C using just a bunch
of macros and the preprocessor to mangle the C++ back into
C so that it could be compiled and run. Debugging was
done on practically unreadable text that vaguely resembled
your original code. By comparison, GOOP actually looks
pretty good. It is written entirely on top of the current
LV language and makes clever use of things like datalog
refnums to make strict types.
Over time I think GOOP will mature, and like typedefs,
some users will come to rely on it in a big way.
Other users will hopefully not even notice that anything
changed. If their project grows in complexity and they
need another tool to manage things, it will be just
another feature that helps them to get useful things done.
Greg McKaskle

Object Oriented Programming concepts

Hi Friends,
I need your help to understand the Object Oriented Programming concepts.
Please help me…
Thanks,
Fl4syed

Hi,
We can learn oops concepts very easily.Refering some books and search this concepts in some websites related to it.I think the author Robert lafore of oops is one of the best way to learn oops concepts.

Concept of object oriented programming

does anyone have notes on concepts of object oriented programming language (Encapsulation,polymorphism,messages,class,inheritance and all that) i tried to find them but i only got definitions for them but i want advantages and disadvantages of concepts also plz can anyone help me

You want the advantages/disadvantages.. hard to find... i got some notes on OO concepts.. u want? Please send me a email to [email protected].. will post it on geocities with the link once u send me the email

Object-oriented programming: state and behaivor

First of all, sorry for my level english.
In Object-Oriented programming, should an object save always some state?
What about session stateless bean service? What is the sense?
These objects have only behaivour and not state.
Perhaps, the sense is that you can send a message to this object, in oposite of a static methods in utility class?
Thanks and regards.

I suppose you could argue that if it doesn't have any state, then it's not really an "object" in the OOP sense, but who cares, really.
Personally, I use state and behavior as a way to help clarify the responsibilities of various classes in the system, and if I see a codebase with a lot of objects with state but no behavior or behavior but no state, then it's a a red flag that it's a messy, poorly-thought-out design (and it usually turns out to be exactly that). The whole point of OOP (IMHO) is encapsulation, and bundling state and behavior together makes things encapsulated (you can prove that state changes only in certain areas in certain circumstances). Encapsulation makes for more easily maintainable code.
It's easy to spot the blue squares in a Mondrian. It's difficult to spot the blue bits in a Pollock. The former is well-encapsulated OOP and the latter is poorly-encapsulated spaghetti code.
That said, it's not the end of the world if you have a static utility class here and there.

Object-Oriented Programming

I'm working on a code associated with object-oriented programming:
The StreetAddress class has this constructor:
StreetAddress( String street, String city,
               String state, String zip );
and the following methods:
void SetStreet( String street ); and String GetStreet();
void SetCity( String city); and String GetCity();
void SetState( String state ); and String GetState();
void SetZIP( String zip ); and String GetZIP();
String MailingLabel();.
The last of these returns the mailing address in the following form:
street
city, state zipand this is what i have so far:
public class StretAddress
private String myStreet;
private String myCity;
private String myState;
private String myZip;
public StreetAddress( String street, String city, String state, String zip)
    myStreet = street;
    myCity = city;
    myState = state;
    myZip = zip;
public String getStreet()
      return myStreet;
public void SetStreet( String street )
    myStreet = street;
public String getCity()
      return myCity;
public void SetCity( String city )
    myCiy = city;
public String getState()
     return myState;
public void SetState( String state )
    myState = state;
public String getZip()
    return myZip;
public void SetZip( String zip )
    myZip = zip;
public String MailingLabel()
System.out.println(street \n city, state + " " + zip);
}I have no idea what to do now, can someone please help me with this?

ejp wrote:
personally, i don't think you need all four in order to be object-oriented.Without all four it might be class-based, or object-based, but not object-oriented. See Peter Wegner's paper which defined all this in 1987:
http://www.cse.msu.edu/~stire/cse891f04/wegner.pdf
With all due respect, I find this "definition" more meaningful:
http://www.youtube.com/watch?v=bfx7tvGisbA

Object Oriented Programming features

Hello,
i want to know more about Object Oriented Programming features, actually i have basic knowledge on Polymorphism, abstraction, DataHidding, Encapsulation, Inheritance. I know the basic bookish definition of these, but can u people give me the definition in terms of java program or any definition which i can co relate with java program.
ex. Class is an example of encapsulation.
Thanks.

RGEO wrote:Hello,
i want to know more about Object Oriented Programming features, actually i have basic knowledge on Polymorphism, abstraction, DataHidding, Encapsulation, Inheritance. I know the basic bookish definition of these, but can u people give me the definition in terms of java program or any definition which i can co relate with java program.
ex. Class is an example of encapsulation.
Thanks.see if we talk about encapsulation ----which means data hiding....now this can b expalined by the following example:
class Rect {
protected int len,br;
public void getdata()
len=14;
br=20;
public int area()
return len*br;
class box extends Rect
private int h;
public void getdata()
super.getdata();
h=56;
System.out.println("the height is :"+h);
public int volume()
return len*br*h;
{color:#ff0000}class inheritance
{color}
{color:#ff0000}public static void main(String[] args)
box obj=new box();
obj.getdata();
System.out.println("volume of box is:"+obj.volume());
}{color}
In the above example we are showing inheritance alongwith encapsulation and it goes like this:
we are able to view the result through main methods i.e. we call our method in main method with the help of objects....so we can say that whatever a user is showing he is showing through main method and not showing the logic because when we complie it then we are only shown the result and not the logic behind it.......This is known as encapsulation----showing relevant features and hiding rest all the things.
Edited by: Namrata.Kakkar on Jul 29, 2009 10:46 PM

Object oriented programming on PXI-System

Greetings,
i've developed some object-oriented LV classes, wich i've succesfully tested on my desktop pc. The next step would have been to test them on a PXI-controller. However, the LV 8.20 methods of object oriented programming seam to be incompatible to PXI-systems.
All i'm getting is an broken arrow with an error message like that
HardwareIOAnalog.lv.class:setTimingNP.vi
Frontpanel-Anschluss 'HardwareIOAnalog in': Der Typ wird für das aktuelle Ziel nicht unterstützt (means: Type not supported by current target)
Does that mean that object-oriented design is not supported in general by PXI, or is it depending on the type of the PXI-System. Is there an easy way around, or do i have to re-program all my classes to conventional (Sub)VIs?
Help appriciated! ;-)
Regards,
Bennet Gedan
Student (Electrical Engineering/Mechatronics)
Darmstadt University of Technology
Bennet Gedan
Student (Electrical Engineering / Mechatronics)
Darmstadt University of Technology

Okay, thanks. Meanwhile I reprogramed the whole thing and set OOP aside (at least on the PXI-Target). It's a pity to loose some advantages of OOP, but it brougth me some interesting new programing techniques i could transfer to non OOP stuff.
Regards,
Bennet Gedan
Student (Electrical Engineering / Mechatronics)
Darmstadt University of Technology

Object oriented programming aspects in Oracle

Dear All,
Can you one explain me the aspects of Object Oriented Programming in Oracle. How to use oops concepts in Oracle Procedures, functions, packages, etc.
Thanks,
Moorthy.GS

Oracle 9i introduces support for inheritance, method overriding and dynamic method dispatch (or "dynamic binding", or "virtual").
A method call is dispatched to the nearest implementation, working back up the inheritance hierarchy from the current or specified type.
See, for example, how we can implement the Template Design Pattern in PL/SQL, using inheritance, method overriding and dynamic method dispatch:
http://www.quest-pipelines.com/pipelines/plsql/tips06.htm#OCTOBER
Oracle 11g introduces support for "super" object-oriented keyword. One attempt to do this in PLSQL 9i/10g:
Calling the Parent Object's Version of an Overridden Method
http://www.quest-pipelines.com/pipelines/plsql/tips03.htm#JUNE
I expect some OO improvements in the future (in Oracle 12oo ...):
1. References between transient objects (instances of objects types) and (then) garbage collector
2. Generic classes (templates, generics) like in Eiffel, C++, Java 5 (PL/SQL was modeled after ADA 83, and ADA 83 has generic packages)
3. Multiple inheritance like in Eiffel (inner classes like in Java - no, please)
4. Design By Contract like in Eiffel (C++ / Java 1.4 assert is not enough)
Design by contract (DBC) is a method whose author is Bertrand Mayer, also maker of OOPL language Eiffel
(Eiffel was designed in 1985, commercialy released in 1986, ISO-standardized in 2006).
Simplified, DBC is based on principle that in each routine (procedure or function) with standard code,
two additional parts – PRECONDITION and POSTCONDITION - need to be asserted.
An additional assertion in class is called INVARIANT.
Contract is based on routine's putting up an obligation to caller (to some other routine)
to satisfy conditions of precondition and conditions of invariant, and hers (called routine's) obligation
to satisfy conditions of postcondition and conditions of invariant.
The object oriented Eiffel programming language was created to implement DBC.
For now, other OO (object-oriented) languages don’t support directly the ideas behind DBC.
However, precondition and postcondition are applicable to many programming languages, both OO and not OO.
Invariants are applicable only in OOPL.
This is my attempt to use DBC methodology (including invariants) in Oracle PL/SQL.
Eiffel class interface (not like Java interface, but more like PL/SQL package specification)
from Bertrand Meyer's book "Object oriented software construction", second edition (OOSC2), 1997, page 390-391:
class interface STACK [G]
creation make
feature -- Initialization
make (n: INTEGER) is -- Alocate stack for a maximum of n elements
    require
      non_negative_capacity: n >= 0
    ensure
      capacity_set: capacity = n
    end
feature -- Access
capacity: INTEGER -- Maximum number of stack elements
count: INTEGER -- Number of stack elements
item: G is -– Top element
    require
      not_empty: not empty
    end
feature -- Status report
empty: BOOLEAN is –- Is stack empty?
    ensure
      empty_definition: Result = (count = 0)
    end
full: BOOLEAN is –- Is stack full?
    ensure
      full_definition: Result = (count = capacity)
    end
feature -- Element change
put (x: G) is –- Add x on top
    require
      not_full: not full
    ensure
      not_empty: not empty
      added_to_top: item = x
      one_more_item: count = old count + 1
    end
remove is -– Remove top element
    require
      not_empty: not empty
    ensure
      not_full: not full
      one_fewer: count = old count - 1
    end
invariant
count_non_negative: 0 <= count
count_bounded: count <= capacity
empty_if_no_elements: empty = (count = 0)
end -– class interface STACK
-- PL/SQL "equivalent":
-- Stack implementation - TABLE of INTEGER.
-- Eiffel has generic classes (like C++ templates and better than Java generics).
-- PL/SQL (now) has not generic classes or generic packages.
CREATE OR REPLACE TYPE array_t AS TABLE OF INTEGER
-- utility package:
CREATE OR REPLACE PACKAGE dbc AS
-- 0 = no check
-- 1 = check preconditions
-- 2 = check preconditions + postconditions
-- 3 = check preconditions + postconditions + invariants
c_no_check                  CONSTANT INTEGER := 0;
c_check_preconditions       CONSTANT INTEGER := 1;
c_check_pre_postconditions CONSTANT INTEGER := 2;
c_check_pre_post_invariants CONSTANT INTEGER := 3;
FUNCTION check_preconditions       RETURN BOOLEAN;
FUNCTION check_pre_postconditions RETURN BOOLEAN;
FUNCTION check_pre_post_invariants RETURN BOOLEAN;
PROCEDURE set_level (p_level INTEGER);
PROCEDURE display_error (p_error VARCHAR2);
END;
CREATE OR REPLACE PACKAGE BODY dbc AS
m_level INTEGER := c_no_check;
FUNCTION check_preconditions RETURN BOOLEAN IS
BEGIN
    IF m_level >= c_check_preconditions THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
FUNCTION check_pre_postconditions RETURN BOOLEAN IS
BEGIN
    IF m_level >= c_check_pre_postconditions THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
FUNCTION check_pre_post_invariants RETURN BOOLEAN IS
BEGIN
    IF m_level >= c_check_pre_post_invariants THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
PROCEDURE set_level (p_level INTEGER) IS
BEGIN
    IF p_level NOT IN
      (c_no_check, c_check_preconditions, c_check_pre_postconditions, c_check_pre_post_invariants)
    THEN
      RAISE_APPLICATION_ERROR (-20000, 'Wrong checking level');
    END IF;
    m_level := p_level;
END;
PROCEDURE display_error (p_error VARCHAR2) IS
BEGIN
    RAISE_APPLICATION_ERROR (-20000, 'ERROR in method ' || p_error);
END;
END;
CREATE OR REPLACE TYPE stack AS OBJECT (
-- Maximum number of stack elements
capacity INTEGER,
-- Number of stack elements
el_count INTEGER,
-- Stack implementation
stack_implementation array_t,
-- Alocate stack for a maximum of n elements
CONSTRUCTOR FUNCTION stack (n INTEGER) RETURN SELF AS RESULT,
-- Top element
MEMBER FUNCTION item (SELF IN OUT stack) RETURN INTEGER,
-- Is stack empty?
MEMBER FUNCTION empty RETURN BOOLEAN,
-- Is stack full?
MEMBER FUNCTION full RETURN BOOLEAN,
-- Add x on top
MEMBER PROCEDURE put (x INTEGER),
-- Remove top element
MEMBER PROCEDURE remove,
-- INVARIANTS
-- Note:
-- If subprogram is declared in an object type body (in PL/SQL 8i/9i/10g)
-- it must be defined in the object type specification too.
MEMBER FUNCTION count_non_negative RETURN BOOLEAN,
MEMBER FUNCTION count_bounded RETURN BOOLEAN,
MEMBER FUNCTION empty_if_no_elements RETURN BOOLEAN,
MEMBER PROCEDURE check_invariants
) NOT FINAL;
CREATE OR REPLACE TYPE BODY stack AS
CONSTRUCTOR FUNCTION stack (n INTEGER) RETURN SELF AS RESULT IS
BEGIN
    IF dbc.check_preconditions AND n < 0 THEN
      dbc.display_error ('stack - PRE');
    END IF;
    check_invariants;
    capacity := n;
    stack_implementation := array_t();
    stack_implementation.EXTEND (n);
    IF dbc.check_pre_postconditions AND capacity <> n THEN
      dbc.display_error ('stack - POST');
    END IF;
    check_invariants;
END;
MEMBER FUNCTION item (SELF IN OUT stack) RETURN INTEGER IS
BEGIN
    IF dbc.check_preconditions AND empty THEN
      dbc.display_error ('item - PRE');
    END IF;
    check_invariants;
    RETURN stack_implementation(el_count);
END;
MEMBER FUNCTION empty RETURN BOOLEAN IS
BEGIN
    IF el_count = 0 THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
MEMBER FUNCTION full RETURN BOOLEAN IS
BEGIN
    IF el_count = capacity THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
MEMBER PROCEDURE put (x INTEGER) IS
BEGIN
    IF dbc.check_preconditions AND full THEN
      dbc.display_error ('put - PRE');
    END IF;
    check_invariants;
    el_count := el_count + 1;
    stack_implementation(el_count) := x;
    -- PL/SQL has not Eiffel's OLD
    -- one_more_item: count = old count + 1
    IF dbc.check_pre_postconditions AND (empty OR item <> x) THEN
      dbc.display_error ('put - POST');
    END IF;
    check_invariants;
END;
MEMBER PROCEDURE remove IS BEGIN
    IF dbc.check_preconditions AND empty THEN
      dbc.display_error ('remove - PRE');
    END IF;
    check_invariants;
    el_count := el_count - 1;
    -- PL/SQL has not Eiffel's OLD
    -- one_fewer: count = old count - 1
    IF dbc.check_pre_postconditions AND full THEN
      dbc.display_error ('remove - POST');
    END IF;
    check_invariants;
END;
-- INVARIANTS
MEMBER FUNCTION count_non_negative RETURN BOOLEAN IS
BEGIN
    IF el_count >= 0 THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
MEMBER FUNCTION count_bounded RETURN BOOLEAN IS
BEGIN
    IF el_count <= capacity THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
MEMBER FUNCTION empty_if_no_elements RETURN BOOLEAN IS
BEGIN
    IF empty AND (el_count = 0)
       OR
       NOT empty AND (el_count <> 0)
    THEN
      RETURN TRUE;
    ELSE
      RETURN FALSE;
    END IF;
END;
MEMBER PROCEDURE check_invariants IS
BEGIN
    IF NOT dbc.check_pre_post_invariants THEN
      RETURN; -- without checking invariants
    END IF;
    IF NOT count_non_negative THEN
      dbc.display_error ('INVARIANT count_non_negative');
    END IF;
    IF NOT count_bounded THEN
      dbc.display_error ('INVARIANT count_bounded');
    END IF;
    IF NOT empty_if_no_elements THEN
      dbc.display_error ('INVARIANT empty_if_no_elements');
    END IF;
END;
END; -- class body STACK
/Regards,
Zlatko Sirotic

Java is a Partially Object-Oriented Programming (True/False)

Hi everybody,
Many of them saying that Java is not purely Object-Oriented Programming.
I am very much confusing on that, so please help me to confirm that "Java is a Partially Object-Oriented Programming Language".

JAVA_NV wrote:
gopivista wrote:
Hi everybody,
Many of them saying that Java is not purely Object-Oriented Programming.
I am very much confusing on that, so please help me to confirm that "Java is a Partially Object-Oriented Programming Language".Java is not purely Object-Oriented Programming,for this two reasons are there
one is we cant create Objects to the primitive data types and there is no multiple Inheritance concept .While there are many definitions of "purely object oriented," and no on widely accepted standard, I've never heard one that requires multiple inheritance. That would NOT be a reason why Java is not fully OO.

Java is pure object oriented programing language or not why?

please clear
java is pure object oriented programing language or not why?

And there is some concepts of object orientation that
Java not implements like: Operator
Overloading and Multiple Heritage. But, i think
that we can live without those features.
And the sucess of Java is a proof of this.I don't believe that operator overloading and multiple inheritance are required aspects of object programming.

Who has the book:Object-Oriented Programming with ABAP Objects

Hello everyone
Now i want to learn ABAP OO,and Lots' of guys told me that the book Object-Oriented Programming with ABAP Objects is realy a good book.but i searched on the net,and could not got PDF of this book,could some one gave me the net address if you know where to download the book or send me to my Mailbox:<email id removed by moderator>,I will very glad to receive any response from you,
of course,if you have some advise on how to learn ABAP OO or some other material ,hope you could share your meaning with me, hope to receive your response.
Best regards!
From Carl
Moderator message : Moved to career center.
Edited by: Vinod Kumar on Aug 27, 2011 9:21 AM

I'm sure you're not asking for illegal, "free" downloads. You can legally purchase the book, also in electronic format, at sap-press.com
Thomas

Do editable a column of a ALV (object oriented programming)

Hello,
How I can do editable a column of a ALV (object oriented programming) ??
What field of a fieldcatalog let it ??
Thanks.
wa_fieldcatalog-fieldname = 'NUM_KGS'.
wa_fieldcatalog-seltext = 'Kg'.
wa_fieldcatalog-coltext = 'Kg'.
wa_fieldcatalog-just = 'L'.
wa_fieldcatalog-tabname = 'IT_DATOS'.
wa_fieldcatalog- ?????????

In the program add the following field
wa_fieldcatalog-EDIT = 'X'.
append wa_fieldcatalog.
you will get the column editable

Trying to understand object oriented programming

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