topic Re: OOPS question in Application Development and Automation Discussions

OOPS question

former_member514536 — Mon, 09 Nov 2020 17:38:43 GMT

how to call the instance construct that is declared in the private section of the class.

class abc definition.

private section.

methods constructor.

endclass.

how to call the above constructor?

Re: OOPS question

BiberM — Mon, 09 Nov 2020 17:47:28 GMT

Beside the fact that a constructor for technically reasons should never be declared Private, your class probably has another static (class-) Method that handles instance creation.

Re: OOPS question

former_member514536 — Mon, 09 Nov 2020 18:21:14 GMT

i know that construct should never be private. But how to answer the above question. it was faced in an interview

Re: OOPS question

matt — Mon, 09 Nov 2020 18:23:48 GMT

a constructor for technically reasons should never be declared Private

Really? What would they be? That's not even a philosophy I've heard of.

Re: OOPS question

BiberM — Mon, 09 Nov 2020 19:46:13 GMT

Well there is even an abapOpenCheck for that which cites the language help:

https://docs.abapopenchecks.org/checks/90/

I can't really rememeber where I encountered that problem ~5 years ago. But changing constructor visibility back to default public solved that.

Re: OOPS question

keremkoseoglu — Tue, 10 Nov 2020 05:07:05 GMT

It actually makes sense to make the constructor private if you are using a creational design pattern; such as:

Builder
Factory
Singleton
Multiton
...

In such cases, the class will typically have a public static method which is responsible of creating an instance. You will call this static public method to create the object instance, instead of calling the constructor.

Check the following example class: https://github.com/keremkoseoglu/addict/blob/main/src/ycl_addict_data_element.clas.abap

This is how you create the object:

DATA(my_obj) = ycl_addict_data_element=>get_instance( 'BUKRS' ).

Instead of this:

DATA(my_obj) = NEW ycl_addict_data_element( 'BUKRS' ). " ERROR!

See?

Re: OOPS question

michael_piesche — Tue, 10 Nov 2020 05:37:14 GMT

>> how to call the above constructor?

Since this is an interview question, which is more about object oriented programming in general than specifically about SAP OO, the answer should be, the following:

In order to create an object of a class with a private constructor, the class needs to have, for example, a public static method which is able to create the object.

class abc definition.
  public section.
    methods create_instance. " method implementation will contain private constructor
  private section.
    methods constructor.
endclass.