Narrow Casting Vs Widening Casting

Former Member — Fri, 18 Mar 2005 09:36:02 GMT

Hello,

Can anybody please explain me the difference with an example between Narrow Casting and Widening Casting in ABAP Objects.

Regards

Kalyan

Re: Narrow Casting Vs Widening Casting

Lakshmant1 — Fri, 18 Mar 2005 10:28:50 GMT

Hi Aswani,

Have a look at this url

http://help.sap.com/saphelp_47x200/helpdata/en/c3/021959f06111d4b2eb0050dadfb92b/frameset.htm

Thanks

Lakshman

Re: Narrow Casting Vs Widening Casting

ssimsekler — Fri, 18 Mar 2005 11:10:01 GMT

Hi Kalyan

In fact, the names imply everything. Let me illustrate a bit. This illustration will deal with one aspect which I think will be enough at least to understand the concept simply. Think of two instances (objects) of two classes one of which is inherited from the other, that is; one is a general class and the other is a specialized class of it.

e.g.

Class 1 --> land_vehicle

Class 2 --> truck

The class land_vehicle has following attributes:


  max_speed
  number_of_wheels
  number_plate
  ...

The class truck has following attributes:


  max_speed [inherited]
  number_of_wheels [inherited]
  number_plate [inherited]
  <i>load_capacity</i> [special to truck class]

Now, assume you have instantiated these classes as

"land_vehicle_obj" and "truck_obj" respectively from these classes.

Between these two objects, you can assign one to the other and at this point casting occurs.

i. If you assign truck_obj to land_vehicle_obj you lose the special attribute load_capacity since you go from the specialized on to the general one. Thus, this is a narrowing cast.

i. If you assign land_vehicle_obj and truck_obj you do not lose any attribute, nevertheless you add a new one. Thus this is a widening cast.

Regards

*--Serdar <a href="https://www.sdn.sap.com:443http://www.sdn.sap.comhttp://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/com.sap.sdn.businesscard.sdnbusinesscard?u=qbk%2bsag%2bjiw%3d">[ BC ]</a>

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Narrow Casting Vs Widening Casting

Re: Narrow Casting Vs Widening Casting

Re: Narrow Casting Vs Widening Casting