topic Re: casting in Application Development and Automation Discussions

casting

Former Member — Mon, 04 Aug 2008 12:51:50 GMT

can anyone tell me something about casting in object oriented programing

Re: casting

Former Member — Mon, 04 Aug 2008 12:59:59 GMT

Hi,

Casting in ABAP OBJECTS is concept related to inheritance.

Narrow Casting: When you assign reference of subclass to reference of superlass, then by superclass reference, you can access the inhertied components of subclass.

Suppose you have a class, lcl_vehicle(reference r_vehicle)

and its subclass lcl_car(r_car).

you have a reference variable:

just have a look at example of narrow casting


DATA: r_vehicle TYPE REF TO lcl_vehicle,
          r_car TYPE REF TO lcl_car.


CREATE OBJECT r_car.

r_vehicle = r_car

Wide Casting: When you assign a superclass reference to subclass reference after narrow casting. Now with this you can access the specific components of subclass.

Have a look at this example


DATA: r_vehicle TYPE REF TO lcl_vehicle,
          r_car TYPE REF TO lcl_car,
          r_car2 LIKE r_car.

CREATE OBJECT r_car.
r_vehicle = r_car.

r_car2 ?= r_vehicle.

'?=' This is wide cast operator.

Now with r_car2 reference you can access inherited as well as specific components of subclass.

Check these links

Regards

Abhijeet

Re: casting

Former Member — Mon, 04 Aug 2008 13:09:59 GMT

hiii...

there are 2 casting in oops concept.

narrow casting and wide casting..

Imagine, you have a Class B inherting from Class A.

The class B is now more specific than A, because it has the methods of A, and can also do more things because it has its own methods.

I have lv_objb type ref to class_b,

lv_obja type ref to class_a.

i create the lv_objb as an object of class b.

But assign this object to lv_obja. This is narrow casting...

which means I have assigne (or cast) a more speicifc object(B) to a generic object (A).

But since you are using a generic object, you have only limited access to the object. You can access only those methos that are defined in A. and hence you have a narrower view of the object B in A. An hence the name narrow cast

The opposite of this is widening cast.

You have create object B. then you narrow cast by assigning it to a variable of type A.

Now i assign this object A to B1 which is also of type B.

So from having a narrow view using A, you have got to a wier view when you assigned to an object B1. hence the name widening cast.

hopefully it will help you a bit...

thanks..

Re: casting

Former Member — Mon, 04 Aug 2008 13:12:31 GMT

Hi,

Please refer to the following links:

http://help.sap.com/saphelp_nw70/helpdata/en/fc/eb3930358411d1829f0000e829fbfe/content.htm

Thanks & regards,

Mayukh

Re: casting

former_member509072 — Mon, 04 Aug 2008 14:07:28 GMT

Casting, in the simplest definition, is assigning of an object of some specific datatype to a variable of some other (technically different, but compatible) datatype.

Keeping this picture in mind, you can re-read and explore what others have already provided in this thread.

-- Zakir

Re: casting

Former Member — Tue, 05 Aug 2008 14:41:31 GMT

hi Abhijeet Kulshr...

thankyou for ur kind information.

with regards.

parthu

Re: casting

Former Member — Tue, 05 Aug 2008 15:05:52 GMT

thank u soo much.

with regards.

bhuma.