Get instance method and design pattern

Hi All,
1. I New to abap objects and i read the help and some stuff from the forum,
l like to now more about design pattern in abap objects,
2. I saw in some abap class the use of method of GET_INSTANCE i think it's from factory pattern , what is the pros. and cons to use this method ,when i should consider to use it ?
Thanks in Advance
Nina

Hello Nina
A very good introduction into design patterns is the book "Head First: Design Patterns". Here you will find many good reasons why and when to use the factory pattern.
You should use the factory pattern when
- you want to prevent "direct" instantiation (i.e. using a public CONSTRUCTOR method) by the developer
- you want to hide the complexity of instantiation from the user of the class
- the instantiation creates an implementation of an interface and you want to keep control of which implementing class is returned
Regards
Uwe

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Singleton Class using a constructor not a get Instance method ?

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Is there any way by which I can return a single instance of the class when the contructor is called ?.
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Pradeep Thomas

Pradeep ,
You see a constructor does not return anything
when you tell java
String str = new String();
It is into the reference str that a Object of the type String is assigned and used ..
If you want a single instance to exist in your application ..the best way is to use the singelton approach.
Alternatively you could create one static instance of the object in a parent class and all the classes that inherit from it will then share access .

Finding instance from variable design pattern required

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Let me explain in deep.
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Hello Nina
A very good introduction into design patterns is the book "Head First: Design Patterns". Here you will find many good reasons why and when to use the factory pattern.
You should use the factory pattern when
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Uwe

How to call Instance Methods and set property values in BAPI?

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Hi,
what version is the SAP PS running? If WebAs or higher, create an inbound synch interface containing your two parameters in the request structure and as many as you require in your response structure. Generate an Inbound ABAP proxy, where you can plug in some code, i.e. create and instantiate an object of the required type and make the call to the BAPI.
If SAP PS on lower than WebAs, then create a wrapper function module and make it RFC enabled. Then plug your code in here and do the same thing.
Watch out for commits!
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Revert back to a polled loop in lieu of Events, use notifiers, occurrences, user-defined events, Producer-consumer loops?
It�s been about 3 years since I have had an application on this level (which used a state machine architecture), and a lot has changed in LabView (using 7.1 Prof Devel). I am currently having a mental block while trying to digest a lot of features I have never used before.
Suggestions Welcome!
Thanks.
~~~~~~~~~~~~~~~~~~~~~~~~~~
"It’s the questions that drive us.”
~~~~~~~~~~~~~~~~~~~~~~~~~~

I suggest a (3) state machine(s) architecture. The first is the user interface. Your main VI is a good start. Another state machine handles the instrument I/O (your serial polling). The third handles all data processing. The three loops run independently. Each has a wait to allow LV's scheduler to share CPU time among the loops. I like queues or functional globals for inter-loop communications.
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Hi
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Rakesh murthy

"
Now my question is, i want to process the data which i get from database. where should i write that processing logic after getting the data from database? in model classes? or in view model classes?
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They're in two of the n layers/tiers.
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Technet articles: Uneventful MVVM;
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Name of the design pattern

Hi
I have been studying a piece of code somebody else wrote. I am wondering if this is the Factory Method design pattern that this represents. I am new to patterns and I would be very thankful for any suggestions.
public class Creator {
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thanks in advance

Yes, you are right this is a Factory Method creational design pattern.
See http://en.wikipedia.org/wiki/Factory_method_pattern for more information.
Ussualy class which is used to create instances of other classe called XXXFactory and implemented as singleton.
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I am new to SAP BI/BW and learned extract and Reports
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thanks
Babu

Hi Babu,
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> Blueprinting -
> High level and detailed design -
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How do I 'call' external instance methods?

I want to send a message from a Controller to another Class to execute a method. Inside the controller, I typed my message:
[[MemoryContent] PopulateMemory];
What I think I am doing here is telling it to go to the MemoryContent class and execute the method called PopulateMemory. The compiler insists that I make PopulateMemory into a class method. But when I do that, I cannot deal with the instance methods and instance variables that I need. What am I missing?

Assuming you are following recommended Cocoa naming conventions, the fact that MemoryContent has an initial cap means it is a class, not an instance of a class. So the compiler error is correct. If you want to use an instance method, first create an instance of the class, then call the method on the instance.
Your method name PopulateMemory should probably not have an initial cap.
So you would typically see something like this.
MemoryContent *memoryContent = [[MemoryContent alloc] init];
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How to study design pattern?

I have learn java for nearly a year and want to know more about design pattern.Fundemanetal instances of basic design pattern are appriciated.Thanks for your answer.

The most famous book on patterns is :
Design Patterns: Elements of Reusable Object-Oriented Software. Gamma et. al.
You should start there if you are interested in the subject.
There are tons of books since then on the subject. There is a list at
http://hillside.net/patterns/books/

Get/set methods

I've been programming in java for a while now, but just recently i started wondering about something. Doesn't get/set methods that contain no other code defeat the point of encapsulation? i.e
public void getXxx() {
return xxx;
But now to the important question. Does the javac compiler inline get/set methods and if yes, how does it work around the private access to the data members?

yes you are right. first all variables should be private (there are some cases where protected is useful). that being hte case, all access methods do is expose the way this class does its storage. and will break if that changes. for example, a rectange using int for width and height, has corresponding setWidth( int ), getHeight() etc. now the author of the class changes int to a Point. now there should only be get/setPoint and the previous should be removed. this changes the API and breaks code using this class.
Lets say one keeps the setWidth etc as 'doing no harm', then the question is why does one need this? commonly used in eg
setWidth( getWidth() + 10 );
to lenghten the width.
A better way is to capture this need in the messaging system. therefore have a method:
widenBy( int w ) {
width += w;
notice this way, when changing the private width variable from int, to Point, to Long or any other, does not break code. there is no need to tidy up the access methods either.
classes that have no behaviour are often created to group variables together and passed along for convenience. These are not strictly classes. Then why not have variables public and save the method calls to access methods. Having access methods does not make it more OO. These 'classes' should be defined as inner classes of the enclosing class.
I've been programming in java for a while now, but
just recently i started wondering about something.
Doesn't get/set methods that contain no other code
defeat the point of encapsulation? i.e

Class methods vs. Instance methods

When shall we use class methods instead of instance methods , and vice versa?
By going through the Java Tutorial, it only says the following.
A common use for static methods is to access static fields....
I am definitely sure that class methods aren't just exist for accessing static fields of a class.
PS. I understand that instance methods belong to the object that is instantiated and class methods belong to the class itself.

Jay-K wrote:
JoachimSauer wrote:
P.S.: I wouldn't call them "class methods". They are called static methods in Java. It helps to stay with the common, widely-used terminology.Thanks, its good to know what the norms are.
but i wonder why the Java Tutorial states it clearly "Class Methods" over here [http://java.sun.com/docs/books/tutorial/java/javaOO/classvars.html|http://java.sun.com/docs/books/tutorial/java/javaOO/classvars.html]
Because strictly speaking that's what they are. They belong to classes, rather than instances of classes. The world-at-large, though, has found that term to be a bit ambiguous, especially when discussing fields - it's not uncommon to see instance variables referred to as "class variables" by newbies - so it's kind-of self-corrected.

Regarding design pattern

Hi,
This is swapna,
I don�t have any idea about design patterns, plz.anybody help me
regarding this, where I can get relevant information about design patterns
Thanks in advance
With regards
Swapna.M

Check http://hillside.net/patterns/onlinepatterncatalog.htm or http://dmoz.org/Computers/Programming/Methodologies/Patterns_and_Anti-Patterns/ for a catalog of online resources about patterns!
Or google for design patterns

Get instance method and design pattern

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