ABAP Objects Design Patterns – Model View Controller (MVC) Part 2

转载自 By Naimesh Patel

In this post, we will see how we can implement the MVC (Model-View-Controller) design pattern in ABAP using the Objects. If you have not read the previous discussion about MVC: ABAP Objects Design Patterns – Model View Controller (MVC) Part 1, than I strongly recommond to read that before moving forward.

Demo Application

To implement the MVC, we will create two applications – One will generate an output in ALV and other will generate an output Smartforms. We will put our business logic in the MODEL class. We will create one CONTROL class to establish control between Model and Views.

Our business logic for this example is fairly simple – select the Sales Orders from the VBAK which were created in last ten days. The public method GET_DATA in the class ZCL_MODEL will act as the business logic. Additionally, this class has the public attribute T_VBAK which will be set by the GET_DATA and hold our data from the table.

UML

The UML diagram for any of the application would be like:

Model Class Setup

Model Method Definition

Model Attribute definition

Code Snippet of method GET_DATA
This code would be implemented in the method GET_DATA

 * Parameters* Importing IR_ERDAT TYPE TPMY_R_DATE Ranges for date*METHOD get_data.** Get data and save into attribute T_VBAK  SELECT * FROM vbak         INTO  TABLE t_vbak         WHERE erdat IN ir_erdat.**ENDMETHOD. 

Controller Class Setup

Our controller class ZCL_CONTROL will have a method GET_OBJECT which will give us an object of the model class. We require a public attribute which can refer to the object created in the method GET_OBJECT.

Controller Method definition:

Controller Attributes definition:

Code Snippet for method GET_OBJECT:

 * Parameters* Importing IF_NAME TYPE CHAR30 Model class name*METHOD get_object .*  DATA: lo_object TYPE REF TO OBJECT.** Generic object reference to importing class  CREATE OBJECT lo_object TYPE (if_name).  IF sy-subrc = 0.*   Downcasting to assign generic object to O_MODEL    o_model ?= lo_object.  ENDIF.*ENDMETHOD. 

In the next post we will see, how we will use the controller class in our view and access the business logic encapsulated in Model class.

Related Links:

• ABAP Objects Design Patterns – Model View Controller (MVC) Part 1
• ABAP Objects Design Patterns – Model View Controller (MVC) Part 3