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Similar to ABAP Object oriented concepts
ABAP Object oriented concepts
- 1. Object Oriented ConceptsObjectOriented Concepts && ABAP ObjectsABAP Objects ByBy Dharmesh KumarDharmesh Kumar
- 2. ObjectivesObjectives • Understand basicconcepts of Object Oriented Programming • Components of a Class • Identify the characteristics of OOP • Implement the characteristics of OOP in ABAP Objects
- 3. Basic concept ofObject Oriented ProgrammingBasic concept of Object Oriented Programming The fundamental idea behind Object Oriented Programming (OOP) is to combine both data and the functions or methods (which operates on that data) into a single unit. Such units, in general terminology, are called Object. OBJECT VEHICLE Plate No Speed Accelerate( ) Show_Speed( ) UNIT
- 4. Need of ObjectOriented ProgrammingNeed of Object Oriented Programming Higher level of abstraction for solving real-life problems Reusability Allows to think in the problem space rather than thinking about data declaration, decisions, loops etc. like in procedural languages. Better control over process visibility
- 5. Components of aClassComponents of a Class There are three components • AttributesAttributes • MethodsMethods • EventsEvents CLASS vehicle DATA : speed TYPE i. METHODS : accelerate, show_speed. EVENTS : seatBeltSign
- 6. Creating class instanceCreatingclass instance Creating a class instance is somewhat similar to creating a data object by taking reference of a data type. DATA : my_var TYPE i. For creating class instance : 1) Data : obj_vehicle TYPE REF TO vehicle. a reference variable of type “pointer to an object of the vehicle class” is created 2) CREATE OBJECT obj_vehicle. an instance of the vehicle class is created a reference to this instance is assigned to “obj_vehicle”
- 7. Type of componentsTypeof components • Static Component • Instance Component Instance components exist separately in each instance (object) of the class. •DATA •METHODS (Can access all attributes and events of their own class) •EVENTS Static components only exist one per class and are valid for all instances of the class. •CLASS-DATA •CLASS-METHODS (Can access only static attributes and static events ) •CLASS-EVENTS •CONSTANTS See Program YCLASS_STATIC (TRZ300)
- 8. Type of componentsContd..Type of components Contd.. Instance Attribute Static Attribute Definition Implementation Instantiation Output
- 9. CLASS (Global +Local)CLASS (Global + Local) Classes can be of two types • Global class • Local class Global vs Local Global Local Accessibility Any program Only within the program where it is defined Stored in Class repository In the program where it is defined Tools to create SE24 Class builder SE38 ABAP Editor Namespace Must begin with ‘Y’ or ‘Z’ Any
- 10. Class declaration (Local)Classdeclaration (Local) CLASS vehicle DEFINITION. DATA speed TYPE I VALUE 0. METHODS: accelerate, show_speed. ENDCLASS. CLASS vehicle IMPLEMENTATION. METHOD accelerate. speed = speed + 1. ENDMETHOD. METHOD show_speed. WRITE speed. ENDMETHOD. ENDCLASS. DEFINITION IMPLEMENTATION
- 11. • The purposeof abstract class is to act as a ‘Model’ for subclasses. • They cannot be instantiated. • To use an abstract class, it has to be inherited in the subclass and its abstract method should redefined. • Abstract methods does not need to implemented in super class Why use abstract class ? An abstract class is used when we want to model an object, the final state of which is not known at the time of modeling and will be known later Abstract ClassAbstract Class
- 12. Abstract Class Contd..AbstractClass Contd.. If a method is declared as abstract, then there is not need to implement it in super class but it needs to be ‘redefined’ in subclass.
- 13. • A classthat is defined as final class can not be inherited further. • All Methods of a final class are inherently final and must not be declared as final in the class definition. • Also, a final method can not be redefined further. • If only a method of a class is final then that class can be inherited but that method cannot be redefined. Why use final class ? If you don't want anyone else to change or override the functionality of your class then you can define it as final. Thus no one can inherit and modify the features of this class. Final ClassFinal Class
- 14. Final Class Contd..FinalClass Contd.. Final Class Final Method Final Subclass method
- 15. Class VariantsClass Variants CLASSclass DEFINITION DEFERRED. When the class needs to be referred before it is being defined. As we have deferred it at the initial stage, the system would not look for this class at higher level context, such as global class library.
- 16. Class Variants Cont..ClassVariants Cont.. CLASS <class> DEFINITION LOAD. •The definition of global classes loads into the memory when a local class is used first time in a program. •When the first access is to a ‘static component’ or in the ‘definition of an event handler method’ then the global class needs to be loaded explicitly into the memory first. CLASS CL_GUI_PICTURE DEFINITION LOAD. CLASS C1 DEFINITION. PUBLIC SECTION. METHODS HANDLER FOR EVENT PICTURE_CLICK OF CL_GUI_PICTURE. ENDCLASS. CLASS C1 IMPLEMENTATION. METHOD HANDLER. ... ENDMETHOD. ENDCLASS.
- 17. Characteristics of ObjectOrientedCharacteristics of Object Oriented languagelanguage 1. Abstraction 2. Encapsulation 3. Inheritance 4. Polymorphism
- 18. AbstractionAbstraction “Abstraction is theelimination of the irrelevant and amplification of the essentials” Everything that is important to the user is visible, but everything that is not, is hidden. Essentials Accelerator Brake Steering wheel Irrelevant Engine mechanism Gear mechanism Brake mechanism
- 19. Visibility All users Subclass methods Class methods PUBLIC XX X PROTECTED X X PRIVATE X EncapsulationEncapsulation ALL USERS CLASS C1 PUBLIC PRIVATE SUBCLASSES of C1 PROTECTED METHODS Encapsulation is Hiding data! Encapsulation is hiding process; hence then you hide the data. Not vice versa
- 20. Encapsulation Contd..Encapsulation Contd.. SeeProgram YCLASS_ENCAP_DEMO (TRZ300) DEFINITION IMPLEMENTATION
- 21. InheritanceInheritance Inheritance is theprocess of creating new classes, called derived classes or subclasses or child classes from existing classes called base classes or super classes or parent classes. The derived class inherits all the capabilities of the base class but can add refinements of its own. The base class is unchanged by this process. VEHICLEVEHICLE accelerate() show_speed() PLANEPLANE accelerate() show_speed() rise() TORPEDOTORPEDO accelerate() show_speed() sink() FIGHTER JETFIGHTER JET accelerate() show_speed() rise() launch_missile()
- 22. Inheritance Contd..Inheritance Contd.. Syntaxfor creating sub classes (local): See Program YCLASS_INHERT_DEMO (TRZ300) For global classes, go to transaction SE24 -> properties tab and define the super class.
- 23. PolymorphismPolymorphism Polymorphism is acharacteristic of being able to assign a different behavior or value in a subclass, to something that was declared in a parent class. VEHICLEVEHICLE accelerate() show_speed() PLANEPLANE accelerate() show_speed() Redefinition TORPEDOTORPEDO accelerate() show_speed() Redefinition
- 24. Polymorphism Contd..Polymorphism Contd.. SeeProgram YCLASS_POLY_DEMO (TRZ300) (Using inheritance) Method Redefinition
- 25. ConstructorConstructor A constructor isa special method which is automatically executed by the runtime environment. They are used to set an object dynamically to a defined initial state. There are two type of constructor 1. Instance Constructor They are called once for each instance after the complete creation of the instance with the CREATE OBJECT statement. 2. Static Constructor They are called in a program once for each class before the class is accessed for the first time.
- 26. Call components (static+ instance)Call components (static + instance) • Attributes Call instance attribute of an object Static attribute of an object oref->attr Static attribute of a class class=>attr Its own instance attribute Its own static attribute me->attr OR attr • Methods Call instance method of an object Static method of an object CALL METHOD oref->meth Static method of a class CALL METHOD class=>meth Its own instance method Its own static method CALL METHOD me->meth OR CALL METHOD meth
- 27. Interfaces • Interfaces extendsscope of a class by adding there own components to the class. • Interfaces can only be defined in ‘PUBLIC SECTION’ of class definition. • Interfaces do not have an implementation part or instance. • Interfaces can be implemented by different classes and its methods can be implemented differently in each class. • Interface components can be called directly after assigning class reference to interface reference. (<iref> = <cref> )
- 28. Type of InterfacesTypeof Interfaces • Local Interface • Global Interface
- 29. Local Interface Interface <intf> Methodmeth1 Endinterface Class <class> definition PUBLIC SECTION Interfaces <intf> METHODS : meth1 Endclass Class <class> implementation method <intf>~meth1 endmethod method meth1 endmethod Endclass 1. Define Interface 2. Declare in class 3. Implement Interface methods
- 30. Local Interface Alias Aliasesare short names given to methods of interfaces for easy access. Interface <interface> Method method Endinterface Class <class> definition Interfaces <interface>. Aliases : m1 FOR <interface>~method Endclass CALL METHOD <class>->interface~method. CALL METHOD <class>->m1.
- 31. Interface Contd.. Both localand global interfaces can be accessedBoth local and global interfaces can be accessed using the following waysusing the following ways Class reference variable CALL METHOD <cl>CALL METHOD <cl>->-><intf>~<meth><intf>~<meth> • Using alias : CALL METHOD <cl>CALL METHOD <cl>->-><meth><meth> Interface reference variable <intf>= <cref> (class reference) CALL METHOD <intf>CALL METHOD <intf>->-><meth><meth>
- 32. Interface Contd.. • Forstatic components only CONSTANT can be accessed using interface name <intf>=><const> • Other STATIC COMPONENTS cannot be accessed using interface name but only through class. Access static attribute <class>=><intf~attr> Access static method CALL METHOD <class>=><intf~meth>
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