OOP
OOP
- Understand the details of object-oriented syntax elements in ABAP Objects and use these effectively
 - Create object-oriented models of business applications
 - Use the tools in the ADT 2.70 to develop object-oriented applications
 
what problems we were having in Procedural programming.
- Long code due to variable declaration
 - Extensive processing after SQL statement
 - Multiple Commands to perform simple operations
 - Code reusability and Maintenance
 
SAP’s solution
- In-line declaration
 - SQL Expressions
 - ABAP Expressions
 - OOP
 
Advantages of OOP over Procedural programming
- Improved software structure and consistency in the development process
 - Reduced maintenance efforts and less susceptibility to errors
 - Better integration of the customer/user into the analysis, design, and maintenance process
 - Easier and safer possibilities for extending the software
 
OOP in ABAP
- Essentially the same as those of other modern object-oriented languages like C++ or Java
 - Some elements present in ABAP objects are not offered in C++ and Java
 - Some specific features of ABAP objects only exist because of the guaranteed downward compatibility of older ABAP language elements
 
OOP Model of ABAP Objects
- ABAP Objects statements can be used in procedural ABAP programs
 - Objects (classes) contain procedural ABAP statements
 - In the object-oriented context :
 
- Only object-oriented concepts that have been proven useful
 - Increased use of type checks
 - Obsolete statements are prohibited
 
OOP Model of ABAP Objects Example
| OOP Model Of ABAP | 
Class and objects
Class:
General Description of Objects
- Specifies status data (attributes) and behavior (methods)
 - Example: Person, Employee
 
Object:
Representation of section of the real world
- Concrete form/specimen/instance of a class
 - Example: Xed, Shayne
 
Attributes
Public Attributes
- Generally Visible
 - Generally Changeable
 - Exception: READ-ONLY Addition
 
Protected Attributes
- accessible to all methods of the class and of classes that inherit from it.
 
Private Attributes
Attributes
Static Attributes
- Exist per class
 - Can be called without instantiation
 - Definition with CLASS-DATA
 
Instance Attributes
- Exist per instance
 - Can only be called if class is instantiated
 - Defined with DATA
 
Methods
- Internal procedures in classes that determine the behavior of the objects
 - Can access all attributes in their class and can therefore change the state of other elements
 - Methods have a signature (interface parameters) that enables them to receive values when they are called and pass back values back to the calling program
 
| Method | 
Interface Parameters
- Can have any number of IMPORTING, EXPORTING, CHANGING, and RETURNING VALUE parameters
 - All parameters can be passed by value or reference
 - Input parameters can be mandatory or OPTIONAL parameters with a DEFAULT value
 
| Interface Parameter | 
Methods
- Public Methods
 
         Can generally be called outside the class
- Protected Methods
 
         Can be called within the class and subclass.
- Private Methods
 
         Can only be called within the class
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