Constructors in OOPS ABAP
Hey Everyone, We have discussed Events in our previous part.
let’s understand about Constructors :-
Constructors :-
- Constructor is a special type of method which is executed automatically when a object is created.
- They can not be called using the CALL METHOD statement.
- Constructors are methods with a predefined name.
- Multiple CONSTRUCTOR and CLASS_CONSTRUCTOR are not allowed with in a class.
Note :- Open any class in SE24(Class Builder ) transaction code.
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We can see there are basically two types of Constructors.
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Click on both the constructors.
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It will be added automatically into your method section.
- We can see, now both the constructors are not available on the top right section indicating that, we cannot have Multiple Constructor and Class Constructors at the same time.
- let’s differentiate both of them.
Types of Constructors :-
1. Constructor ( Instance Constructor ) :-
- It has only importing parameters.
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Select Instance Constructor and click on parameters.
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In the above diagram we can clearly see that we can only have importing parameters for Instance constructors.
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- It can access both static and Instance attributes.
- It is called every time when a object is created.
- Used to set default value for a particular instance.
2. CLASS_CONSTRUCTOR ( Static Constructor ) :-
- Name of the method :- CLASS_CONSTRUCTOR
- It does not have any parameters.
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Select the class constructor we and click on parameters.
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We will get a notification message that we cannot have any parameters for our class constructor.
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- It can access only static attributes.
- It is called first time when a object is created.
let’s have some implementation for both these methods so that we can understand it more clearly.
- Step 1 :- Click on the attributes tab and let’s create two instance attributes and one static attributes.
- Step 2 :- now click on the source code of instance constructor.
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Step 3 :- Now go to the source code of CLASS_CONSTRUCTOR.
- As soon as I am trying to access the instance attributes inside a class constructor, We will get a error message.
- now, you can see it is working perfectly fine.
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Step 4:- Go to ABAP Editor ( SE38) and create object for our class.
Executing the program :-
- Press F8 to execute the program.
- Now, let’s see and analysis
- We can see clearly that our Class constructor executed before the Instance constructor and it gets executed only once.
- However our instance constructor will be executed every time when we will create any object.
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