Difference between abap object and function

Question

hi all,
i read the book on abap object of the difference between abap object and classical abap.
i know that there is only 1 instance of a specific function group but somehow i still not so clear why subsequent vehicle cannot use the same function. i also can use the do and loop to call the function? if cannot then why?
hope can get the advice.
thanks
using function *********
function-pool vehicle.
data speed type i value 0.
function accelerate.
speed = speed + 1.
endfunction.
function show_speed.
write speed.
endfunction.
report xx.
start-of-selection.
*vehicle 1
call function 'accelerate'.
call function 'accelerate'.
call function 'show_speed'.
*vehicle 2
*vehicle 3
*****abap object*******
report xx.
data: ov type ref to vehicle,
         ov_tab type table of ref to vehicle.
start-of-selection.
do 5 times.
create object ov.
append ov to ov_tab.
enddo.
loop at ov_tab into ov.
do sy-tabix times.
call method ov->accelerate.
enddo.
call method ov->show_speed.
endloop.

Answer 1

Hi
Now try this:
REPORT ZTEST_VEHICLEOO .
PARAMETERS: P_CAR   TYPE I,
            P_READ  TYPE I.
*       CLASS vehicle DEFINITION
CLASS VEHICLE DEFINITION.
  PUBLIC SECTION.
    CLASS-DATA: MAX_SPEED   TYPE I,
                MAX_VEHICLE TYPE I,
                NR_VEHICLES TYPE I.
    CLASS-METHODS CLASS_CONSTRUCTOR.
    METHODS CONSTRUCTOR.
    METHODS ACCELERATE.
    METHODS SHOW_SPEED.
    METHODS GET_SPEED EXPORTING E_SPEED TYPE I.
  PRIVATE SECTION.
    DATA: SPEED      TYPE I,
          NR_VEHICLE TYPE I..
ENDCLASS.
*       CLASS vehicle IMPLEMENTATION
CLASS VEHICLE IMPLEMENTATION.
  METHOD CLASS_CONSTRUCTOR.
    NR_VEHICLES = 0.
  ENDMETHOD.
  METHOD CONSTRUCTOR.
    NR_VEHICLES = NR_VEHICLES + 1.
    NR_VEHICLE  = NR_VEHICLES.
  ENDMETHOD.
  METHOD ACCELERATE.
    SPEED = SPEED + 1.
    IF MAX_SPEED < SPEED.
      MAX_SPEED   = SPEED.
      MAX_VEHICLE = NR_VEHICLE.
    ENDIF.
  ENDMETHOD.
  METHOD SHOW_SPEED.
    WRITE: / 'Speed of vehicle nr.', NR_VEHICLE, ':', SPEED.
  ENDMETHOD.
  METHOD GET_SPEED.
    E_SPEED = SPEED.
  ENDMETHOD.
ENDCLASS.
DATA: OV     TYPE REF TO VEHICLE,
      OV_TAB TYPE TABLE OF REF TO VEHICLE.
DATA: V_TIMES TYPE I,
      FL_ACTION.
DATA: V_SPEED TYPE I.
START-OF-SELECTION.
  DO P_CAR TIMES.
    CREATE OBJECT OV.
    APPEND OV TO OV_TAB.
  ENDDO.
  LOOP AT OV_TAB INTO OV.
    IF FL_ACTION = SPACE.
      FL_ACTION = 'X'.
      V_TIMES = SY-TABIX * 2.
    ELSE.
      FL_ACTION = SPACE.
      V_TIMES = SY-TABIX - 2.
    ENDIF.
    DO V_TIMES TIMES.
      CALL METHOD OV->ACCELERATE.
    ENDDO.
    CALL METHOD OV->SHOW_SPEED.
  ENDLOOP.
  SKIP.
  WRITE: / 'Higher speed', VEHICLE=>MAX_SPEED, 'for vehicle nr.',
            VEHICLE=>MAX_VEHICLE.
  SKIP.
  READ TABLE OV_TAB INTO OV INDEX P_READ.
  IF SY-SUBRC <> 0.
    WRITE: 'No vehicle', P_READ.
  ELSE.
    CALL METHOD OV->GET_SPEED IMPORTING E_SPEED = V_SPEED.
    WRITE: 'Speed of vehicle', P_READ, V_SPEED.
  ENDIF.
Try to repeat this using a function group and I think you'll undestand because it'll be very hard to do it.
By only one function group how can u read the data of a certain vehicle?
Yes you can create in the function group an internal table where u store the data of every car: in this way u use the internal table like it was an instance, but you should consider here the example is very simple. Here we have only the speed as characteristic, but really we can have many complex characteristics.
Max