Re: class methods

ashok_kumar24 — Wed, 09 May 2007 07:41:04 GMT

Hai Sai,

Good ... Check out the following examples

Define, implement and use simple class

***INCLUDE ZBC404_HF_LCL_AIRPLANE .

******************************************

Definition part

******************************************

CLASS lcl_airplane DEFINITION.

*----

Public section

*----

PUBLIC SECTION.

TYPES: t_name(25) TYPE c.

METHODS:

constructor,

set_attributes IMPORTING p_name TYPE t_name

p_planetype TYPE saplane-planetype,

display_attributes,

display_n_o_airplanes.

*----

Private section

*----

PRIVATE SECTION.

Private attributes

DATA: name(25) TYPE c,

planetype TYPE saplane-planetype.

Private static attribute

CLASS-DATA n_o_airplanes TYPE i.

ENDCLASS.

******************************************

Implementation part

******************************************

CLASS lcl_airplane IMPLEMENTATION.

METHOD constructor.

Counts number of instances

n_o_airplanes = n_o_airplanes + 1.

ENDMETHOD.

METHOD set_attributes.

name = p_name.

planetype = p_planetype.

ENDMETHOD.

METHOD display_attributes.

WRITE:/ 'Name:', name, 'Planetype:', planetype.

ENDMETHOD.

METHOD display_n_o_airplanes.

WRITE: / 'No. planes:', n_o_airplanes.

ENDMETHOD.

ENDCLASS.

REPORT zbc404_hf_maintain_airplanes .

INCLUDE zbc404_hf_lcl_airplane.

Create reference to class lcl_airplane

DATA: airplane1 TYPE REF TO lcl_airplane,

airplane2 TYPE REF TO lcl_airplane.

START-OF-SELECTION.

Create instance

CREATE OBJECT airplane1.

CALL METHOD: airplane1->display_n_o_airplanes.

CREATE OBJECT airplane2.

Setting attributes using a method with parameters

CALL METHOD airplane1->set_attributes EXPORTING p_name = 'Kurt'

p_planetype = 'MD80'.

END-OF-SELECTION.

Using methods

CALL METHOD: airplane1->display_n_o_airplanes,

airplane1->display_attributes.

The resulting report:

Maintain airplanes

No. planes: 1

No. planes: 2

Name: Kurt Planetype: MD80

Use constructor to create an object with parameters

CLASS lcl_airplane DEFINITION.

PUBLIC SECTION.

TYPES: t_name(25) TYPE c.

METHODS:

constructor importing p2_name type t_name

p2_planetype TYPE saplane-planetype,

..... more code .......

CLASS lcl_airplane IMPLEMENTATION.

METHOD constructor.

name = p2_name.

planetype = p2_planetype.

..... more code .......

START-OF-SELECTION.

CREATE OBJECT airplane1 exporting p2_name = 'Hansemand'

p2_planetype = 'Boing 747'.

Subclassing

This example uses a superclass LCL_AIRPLANE and subclasses it into LCL_PASSENGER_AIRPLANE and LCL_CARGO_PLANE.

LCL_AIRPLANE has a method display_n_o_airplanes that displays the number of object instances.

LCL_PASSENGER_AIRPLANE has the private instance attribute n_o_seats, and redefines the superclass method display_attributes, so it also displays n_o_seats.

LCL_CARGO_PLANE has the private instance attribute cargomax, and redefines the superclass method display_attributes, so it also displays cargomax.

All instance attributes are provided by the cunstructor method.

Superclass LCL_AIRPLANE

***INCLUDE ZBC404_HF_LCL_AIRPLANE .

******************************************

Definition part

******************************************

CLASS lcl_airplane DEFINITION.

*----

Public section

*----

PUBLIC SECTION.

TYPES: t_name(25) TYPE c.

METHODS:

constructor IMPORTING im_name TYPE t_name

im_planetype TYPE saplane-planetype,

display_attributes.

Static methods

CLASS-METHODS:

display_n_o_airplanes.

*----

Protected section

*----

PROTECTED SECTION.

Private attributes

DATA: name(25) TYPE c,

planetype TYPE saplane-planetype.

Private static attribute

CLASS-DATA n_o_airplanes TYPE i.

ENDCLASS.

******************************************

Implementation part

******************************************

CLASS lcl_airplane IMPLEMENTATION.

METHOD constructor.

name = im_name.

planetype = im_planetype.

Counts number of instances

n_o_airplanes = n_o_airplanes + 1.

ENDMETHOD.

METHOD display_attributes.

WRITE:/ 'Name:', name, 'Planetype:', planetype.

ENDMETHOD.

METHOD display_n_o_airplanes.

WRITE: / 'No. planes:', n_o_airplanes.

ENDMETHOD.

ENDCLASS.

Sub class LCL_PASSENGER_AIRPLANE

***INCLUDE ZBC404_HF_LCL_PASSENGER_PLANE .

*******************************************************************

This is a subclass of class lcl_airplane

*******************************************************************

CLASS lcl_passenger_airplane DEFINITION INHERITING FROM lcl_airplane.

PUBLIC SECTION.

The constructor contains the parameters from the superclass
plus the parameters from the subclass

METHODS:

constructor IMPORTING im_name TYPE t_name

im_planetype TYPE saplane-planetype

im_n_o_seats TYPE sflight-seatsmax,

Redefinition of superclass method display_attributes

display_attributes REDEFINITION.

PRIVATE SECTION.

DATA: n_o_seats TYPE sflight-seatsmax.

ENDCLASS.

CLASS lcl_passenger_airplane IMPLEMENTATION.

METHOD constructor.

The constructor method of the superclass MUST be called withing the
construtor

CALL METHOD super->constructor

EXPORTING im_name = im_name

im_planetype = im_planetype.

n_o_seats = im_n_o_seats.

ENDMETHOD.

The redefined display_attributes method

METHOD display_attributes.

CALL METHOD super->display_attributes.

WRITE: / 'No. seats:', n_o_seats.

ENDMETHOD.

ENDCLASS.

Sub class LCL_CARGO_PLANE

***INCLUDE ZBC404_HF_LCL_CARGO_PLANE .

*******************************************************************

This is a subclass of class lcl_airplane

*******************************************************************

CLASS lcl_cargo_plane DEFINITION INHERITING FROM lcl_airplane.

PUBLIC SECTION.

METHODS:

The constructor contains the parameters from the superclass
plus the parameters from the subclass

constructor IMPORTING im_name TYPE t_name

im_planetype TYPE saplane-planetype

im_cargomax type scplane-cargomax,

Redefinition of superclass method display_attributes

display_attributes REDEFINITION.

PRIVATE SECTION.

DATA:cargomax TYPE scplane-cargomax.

ENDCLASS.

CLASS lcl_cargo_plane IMPLEMENTATION.

METHOD constructor.

The constructor method of the superclass MUST be called withing the
constructor

CALL METHOD super->constructor

EXPORTING im_name = im_name

im_planetype = im_planetype.

cargomax = im_cargomax.

ENDMETHOD.

METHOD display_attributes.

The redefined display_attributes method

CALL METHOD super->display_attributes.

WRITE: / 'Cargo max:', cargomax.

ENDMETHOD.

ENDCLASS.

The Main program that uses the classes

REPORT zbc404_hf_main .

Super class

INCLUDE zbc404_hf_lcl_airplane.

Sub classes

INCLUDE zbc404_hf_lcl_passenger_plane.

INCLUDE zbc404_hf_lcl_cargo_plane.

DATA:

Type ref to sub classes. Note: It is not necesssary to make typeref to the superclass

o_passenger_airplane TYPE REF TO lcl_passenger_airplane,

o_cargo_plane TYPE REF TO lcl_cargo_plane.

START-OF-SELECTION.

Display initial number of instances = 0

CALL METHOD lcl_airplane=>display_n_o_airplanes.

Create objects

CREATE OBJECT o_passenger_airplane

EXPORTING

im_name = 'LH505'

im_planetype = 'Boing 747'

im_n_o_seats = 350.

CREATE OBJECT o_cargo_plane

EXPORTING

im_name = 'AR13'

im_planetype = 'DC 3'

im_cargomax = 35.

Display attributes

CALL METHOD o_passenger_airplane->display_attributes.

CALL METHOD o_cargo_plane->display_attributes.

Call static method display_n_o_airplanes
Note: The syntax for calling a superclass method, differs from the syntax when calling a subclass method.
When calling a superclass => must be used instead of ->

CALL METHOD lcl_airplane=>display_n_o_airplanes.

Result:

No. planes: 0

Name: LH505 Planetype: Boing 747

No. seats: 350

Name: AR13 Planetype: DC 3

Cargo max: 35,0000

No. planes: 2

Polymorphism

Polymorphism: When the same method is implemented differently in different classes. This can be done using enheritance, by redefining a method from the superclass in subclasses and implement it differently.

Classes:

lcl_airplane Superclass

lcl_cargo_airplane Subclass

lcl_passenger_airplane Subclass

The method estimate_fuel_consumption is implemented differently in the 3 classes, as it depends on the airplane type.

Object from different classes are stored in an internal table (plane_list) consisting of references to the superclass, and the processed

identically for all the classes.

What coding for the estimate_fuel_consumption method taht is actually executed, depends on the dynamic type of the plane reference variable,

that is, depends on which object plane points to.

DATA: cargo_plane TYPE REF to lcl_cargo_airplane,

passenger_plane TYPE REF to lcl_passenger_airplane,

plane_list TYPE TABLE OF REF TO lcl_airplane.

Creating the list of references

CREATE OBJECT cargo_plane.

APPEND cargo_plane to plane_list.

CREATE OBJECT passenger_plane

APPEND passenger_plane to plane list.

Generic method for calucalting required fuel

METHOD calculate required_fuel.

DATA: plane TYPE REF TO lcl_airplane.

LOOP AT plane_list INTO plane.

re_fuel = re_fuel + plane->estimate_fuel_consumption( distance ).

ENDLOOP.

ENDMETHOD.

Working example:

This example assumes that the classes lcl_airplane, lcl_passnger_airplane and lcl_cargo plane (Se Subcallsing) exists.

Create objects of type lcl_cargo_plane and lcl_passenger_airplane, adds them to a list in lcl_carrier, and displays the list.

&----

*& Include ZBC404_HF_LCL_CARRIER *

*& *

&----

CLASS lcl_carrier DEFINITION *

----

CLASS lcl_carrier DEFINITION.

PUBLIC SECTION.

TYPES: BEGIN OF flight_list_type,

connid TYPE sflight-connid,

fldate TYPE sflight-fldate,

airplane TYPE REF TO lcl_airplane,

seatsocc TYPE sflight-seatsocc,

cargo(5) TYPE p DECIMALS 3,

END OF flight_list_type.

METHODS: constructor IMPORTING im_name TYPE string,

get_name RETURNING value(ex_name) TYPE string,

add_a_new_airplane IMPORTING

im_airplane TYPE REF TO lcl_airplane,

create_a_new_flight importing

im_connid type sflight-connid

im_fldate type sflight-fldate

im_airplane type ref to lcl_airplane

im_seatsocc type sflight-seatsocc

optional

im_cargo type p optional,

display_airplanes.

PRIVATE SECTION.

DATA: name TYPE string,

list_of_airplanes TYPE TABLE OF REF TO lcl_airplane,

list_of_flights TYPE TABLE OF flight_list_type.

ENDCLASS.

----

CLASS lcl_carrier IMPLEMENTATION

----

CLASS lcl_carrier IMPLEMENTATION.

METHOD constructor.

name = im_name.

ENDMETHOD.

METHOD get_name.

ex_name = name.

ENDMETHOD.

METHOD create_a_new_flight.

DATA: wa_list_of_flights TYPE flight_list_type.

wa_list_of_flights-connid = im_connid.

wa_list_of_flights-fldate = im_fldate.

wa_list_of_flights-airplane = im_airplane.

IF im_seatsocc IS INITIAL.

wa_list_of_flights-cargo = im_cargo.

ELSE.

wa_list_of_flights-seatsocc = im_seatsocc.

ENDIF.

APPEND wa_list_of_flights TO list_of_flights.

ENDMETHOD.

METHOD add_a_new_airplane.

APPEND im_airplane TO list_of_airplanes.

ENDMETHOD.

METHOD display_airplanes.

DATA: l_airplane TYPE REF TO lcl_airplane.

LOOP AT list_of_airplanes INTO l_airplane.

CALL METHOD l_airplane->display_attributes.

ENDLOOP.

ENDMETHOD.

ENDCLASS.

REPORT zbc404_hf_main .

*******************************************************************

This reprort uses class LCL_AIRPLNAE and subclasses
LCL_CARGO_PLANE and LCL_PASSENGER_AIRPLANE and class LCL_CARRIER

*******************************************************************

Super class for airplanes

INCLUDE zbc404_hf_lcl_airplane.

Sub classes for airplanes

INCLUDE zbc404_hf_lcl_passenger_plane.

INCLUDE zbc404_hf_lcl_cargo_plane.

Carrier class

INCLUDE zbc404_hf_lcl_carrier.

DATA:

Type ref to classes

o_passenger_airplane TYPE REF TO lcl_passenger_airplane,

o_passenger_airplane2 TYPE REF TO lcl_passenger_airplane,

o_cargo_plane TYPE REF TO lcl_cargo_plane,

o_cargo_plane2 TYPE REF TO lcl_cargo_plane,

o_carrier TYPE REF TO lcl_carrier.

START-OF-SELECTION.

Create objects

CREATE OBJECT o_passenger_airplane

EXPORTING

im_name = 'LH505'

im_planetype = 'Boing 747'

im_n_o_seats = 350.

CREATE OBJECT o_passenger_airplane2

EXPORTING

im_name = 'SK333'

im_planetype = 'MD80'

im_n_o_seats = 110.

CREATE OBJECT o_cargo_plane

EXPORTING

im_name = 'AR13'

im_planetype = 'DC 3'

im_cargomax = 35.

CREATE OBJECT o_cargo_plane2

EXPORTING

im_name = 'AFL124'

im_planetype = 'Iljutsin 2'

im_cargomax = 35000.

CREATE OBJECT o_carrier

EXPORTING im_name = 'Spritisch Airways'.

Add passenger and cargo planes to the list of airplanes

CALL METHOD o_carrier->add_a_new_airplane

EXPORTING im_airplane = o_passenger_airplane.

CALL METHOD o_carrier->add_a_new_airplane

EXPORTING im_airplane = o_passenger_airplane2.

CALL METHOD o_carrier->add_a_new_airplane

EXPORTING im_airplane = o_cargo_plane.

CALL METHOD o_carrier->add_a_new_airplane

EXPORTING im_airplane = o_cargo_plane2.

Display list of airplanes

call method o_carrier->display_airplanes.

Result:

Name: LH505 Planetype: Boing 747

No. seats: 350

Name: SK333 Planetype: MD80

No. seats: 110

Name: AR13 Planetype: DC 3

Cargo max: 35,0000

Name: AFL124 Planetype: Iljutsin 2

Cargo max: 35.000,0000

Events

Below is a simple example of how to implement an event.

REPORT zbc404_hf_events_5.

----

CLASS lcl_dog DEFINITION

----

CLASS lcl_dog DEFINITION.

PUBLIC SECTION.

Declare events

EVENTS:

dog_is_hungry

EXPORTING value(ex_time_since_last_meal) TYPE i.

METHODS:

constructor

IMPORTING im_name TYPE string,

set_time_since_last_meal

IMPORTING im_time TYPE i,

on_dog_is_hungry FOR EVENT dog_is_hungry OF lcl_dog

IMPORTING ex_time_since_last_meal.

ENDCLASS.

----

CLASS lcl_dog IMPLEMENTATION

----

CLASS lcl_dog IMPLEMENTATION.

METHOD constructor.

WRITE: / 'I am a dog and my name is', im_name.

ENDMETHOD.

METHOD set_time_since_last_meal.

IF im_time < 4.

SKIP 1.

WRITE: / 'You fool, I am not hungry yet'.

ELSE.

Subsrcribe for event:
set handler <Event handler method>
FOR <ref_sender>!FOR ALL INSTANCES [ACTIVATION <var>]

SET HANDLER on_dog_is_hungry FOR ALL INSTANCES ACTIVATION 'X'.

Raise event

RAISE EVENT dog_is_hungry

EXPORTING ex_time_since_last_meal = im_time.

ENDIF.

ENDMETHOD.

METHOD on_dog_is_hungry.

Event method, called when the event dog_is_hungry is raised

SKIP 1.

WRITE: / 'I have not eaten for more than',

ex_time_since_last_meal, ' hours'.

WRITE: / 'Give me something to eat NOW!'.

ENDMETHOD.

ENDCLASS.

----

R E P O R T

----

DATA: o_dog1 TYPE REF TO lcl_dog.

START-OF-SELECTION.

CREATE OBJECT o_dog1 EXPORTING im_name = 'Beefeater'.

CALL METHOD o_dog1->set_time_since_last_meal

EXPORTING im_time = 2.

This method call will raise the event dog_is_hungy
because time > 3

CALL METHOD o_dog1->set_time_since_last_meal

EXPORTING im_time = 5.

Good Luck and thanks

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