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ABAP OO Example
- Details
- Category: ABAP
- Published on Wednesday, 12 September 2007 22:55
- Written by Henrik Frank
- Hits: 12970
Define, implement and use simple class | Use constructor to create an object with parameters | Subclassing | Polymorphism | Events
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 u
sing 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 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: / 'You son of a LLLL. 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.Result:
I am a dog and my name is Beefeater
You fool, I am not hungry yet
You son of a LLLL. I have not eaten for more than 5 hours
Give me something to eat NOW!
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