Constructors are special methods that are called automatically while creating an object or instantiated (accessing the class components) first time.
Constructor gets triggered when an object is created.
To trigger a method, we need to call a method. CONSTRUCTORS are two types and those are –
| Constuctor Types | Description |
|---|---|
| Instance constructor | Instance constructor methods can only have importing parameters and there will not be any exporting parameters. The name of the CONSTRUCTOR method must be CONSTRUCTOR only. |
| Static constructor | Static constructors are mainly used to set the default values globally irrespective of instances/methods. These methods will not have any importing and exporting parameters. Static constructor methods gets executed only once. The name of the CLASS CONSTRUCTOR must be CLASS_CONSTRUCTOR. |
Example –
Simple example to explain how the constructor is being triggered.
Code –
*&---------------------------------------------------------------------*
*& Report Z_CONSTRUCTORS
*&---------------------------------------------------------------------*
*& Written by TutorialsCampus
*&---------------------------------------------------------------------*
REPORT Z_CONSTRUCTORS.
* Class & methods definition
CLASS classnew DEFINITION.
PUBLIC SECTION.
* Instance constructor definition
METHODS constructor.
* Static constructor definition
CLASS-METHODS class_constructor.
ENDCLASS.
* Class & method implementation
CLASS classnew IMPLEMENTATION.
* Instance method implementation
METHOD constructor.
WRITE:/ 'Instance Constructor Triggered'.
ENDMETHOD.
* Static method implementation
METHOD class_constructor.
WRITE:/ 'Static Constructor Triggered'.
ENDMETHOD.
ENDCLASS.
START-OF-SELECTION.
* Defining object objectnew for the class classnew
DATA: objectnew TYPE REF TO classnew.
* Creating object objectnew
CREATE OBJECT objectnew.
Output –
Explaining Example –
In the above example, each and every statement is preceeded with a comment to explain about the statement. Go through them to get clear understanding of example code.
constructor is instance constructor as it was defined by using METHODS clause. class_constructor is static constructor as it was created by using CLASS-METHODS clause.
The static and instance constructors are called when the object objectnew is created. Static constructor is the first constructor triggered before and instance constructor triggered.