Working with constructors (Global Class)

1.     Constructors are special methods that cannot be called using CALL METHOD. Instead, they are called automatically by the system to set the starting state of a new object or class.

2.     Constructors are methods with a predefined name. To use them, you must declare them explicitly in the class.

3.     There are two types of constructors - Instance constructors and Static constructors.  

·         The Instance constructor of a class is the predefined instance method CONSTRUCTOR.

·         The constructor's signature can have only importing parameters or exceptions.

·         Instance Constructor is a special instance method can access the Instance Variables and Static Variables.

·         This method is used to set the default values in a class.         

·         The Static constructor of a class is the predefined static method CLASS_CONSTRUCTOR.

·         The constructor's signature cannot have importing parameters or exceptions.

·         The static constructor is as special static method can access the static variables.

·         These are used to set default values for the global attributes irrespective of instances.

·         Multiple Instance and Static Constructors cannot be used in one class.  

Creating the Instance Constructor and Static Constructor using SE24 (Global class)

Step1: Go to SE24 à Create Global Class ZCONSTRUCTOR_SALES

 

Step2: Select the Class and Click on Continue.

 

Step3: Continue with the default settings

 

Step4: Go to Methods à Create Methods.

Step5: Constructor Method can be created 2 ways.

1)     Go to Menu à Edit à Create Constructor

2)     Click on Constructor as shown below  

Step6: As soon click on Constructor à Constructor Method is automatically defaulted in the Methods.

This method is used o initial the values for the object

Step7: Create another method Select to fetch the data from the VBAK table

Step8: Select the Constructor Method à Select the Parameters and Create the Parameter

Step9: The parameter IM_VBELN is used to importing into Constructor Method. Used to initialize the value

Step10: For the Constructor, parameter type is always importing. No other Parameter type can be assigned

 

Step11: Go to Type Tab à Create Structure ty_vbak and Visibility (Public)

Step12: Click on Direct Type Entry

Step13: To declare the Structure (with required fields) and Table

Step13: To declare the Structure (with required fields) and Table

Step14:  t_vbak is defaulted in the Types tab which has be declared in earlier step

Step15: In the Attributes Tabà Create V_VBELN type vbak-vbeln.

Step16: Double click the Constructor and Implement the code.

Step17:  Go to Select Method à Create Parameters

Step18:  Go to Select Method à Double Click the Method and Implement the code

Step18:  Activate the Class and Go to SE38 à Create a Program: ZCONSTRUCTOR_SALES.

Implement the code and execute the Program

Step20:  Execute the Program without giving any sales document number.

 

Step21:  The Output is displayed as shown below with the Constructor method with the default initial values

Step22:  Give the Sales Document as: 4971

 

Step23:  The output is displayed for the corresponding Sales document

Static Constructor  

Step24: Within the Same Global Class Create the Static Constructor. Click on Class Constructor

                                          OR

Menu à Edit à Create Class Constructor.

Step25: Class Constructor Method is defaulted as shown below as soon as the Class Constructor is Clicked or Selected.

Step26: Select the Class Constructor and Click on Parameters à following message is displayed.

Class Constructor does not have Parameters.

Step27: Double Click the Class_Constructor method and write the Write Statement

Step28: Go to SE38 and execute the same program ZCONSTRUCTOR_SALES. The Class Constructor is triggered.