How to create data for a child class from another data class using an operation

This ‘How-to’ provides information on how to use an operation to create data for a child data class from a different data class. For example, from a data class that is not a parent of the child class. Operations are similar to methods.

Operations are stateless – within an operation, the current content is being ‘read’. For example, the class data is not yet available.
Methods are stateful – within a method, the current context is being ‘worked with’. For example, the properties within the class are already available.

The following development process demonstrates how to add data to the child class (MYCLASS1.CL1) of a data class (MYCLASS1) from a different data class (MYCLASS2), by adding a simple script to create an operation on (MYCLASS1) which is called from (MYCLASS2):

Open your data class (MYCLASS1).
Select the Methods tab > Methods block, and set the following field values:

Code: Enter a new method code (MYMETH1).

Description: Enter a description for the method.

Return type: Select an appropriate return type.

Operation: Select this option (yes). This will automaticallygenerate the keys ( Keys block).
Enter parameters (MYPARAM1) which need to be passed ( Parameter definitions block).
Select the General tab > Scripts block, and set the following field values:

Type: Select a type appropriate for your script.

Scripts: Accept the displayed default code. This is automatically generated using the class code and script type. Alternatively, enter a unique code for your script.

Running order: Accept the displayed numeric value. This is automatically generated to control the order in which the '$PROPERTIES' and '$METHODS' labels are called in the event. Alternatively, enter the running order code for your script.
To add your script, right-click the Scripts code and select Processing editor from the selection menu. Enter the source code (see below):

Note: This example will use the key (Methods tab > Keys block) which is passed to read the current context from 'MYCLASS1' and then update the property (PROP1) using the parameter 'MYPARAM1' which is passed to it.

$Structure MYCLASS1

##########################################
#             METHODS                    #
##########################################
$METHODS
  Case CURPTH
    When ""
        Case ACTION
           When "MYMETHOD" Gosub MYMETHOD  # Update MYPROP1 method 
        Endcase  
  Endcase
Return

# Update MYPROP1 using MYPRAM1 which is passed
# KEY1 and MYPARAM1 are passed and used in this operation

$MYMETHOD
   Local Integer NEWLINE
    # Use standard method CRUD to read MYCLASS1
    ASTATUS=fmet this.AREAD(MYCLASS1)
    If ASTATUS<>[V]CST_AOK
      ARET_VALUE= CST_AFALSE
      Return
    Else
      ARET_VALUE= CST_ATRUE
      # create a new line for MYCLASS1.CL1 at last position
      NEWLINE=fmet this.ADDLINE("CL1",[V]CST_ALASTPOS)
      If NEWLINE=[V]CST_ANOTDEFINED # check status after creating line
        ARET_VALUE = CST_AFALSE
      Endif

      If ARET_VALUE = CST_ATRUE
        # update CL1 with values passed 
        this.CL1(NEWLINE).MYPROP1 = MYPARAM1
        ASTATUS=fmet this.AUPDATE
        If ASTATUS<>[V]CST_AOK
          ARET_VALUE= CST_AFALSE
        Endif
      Endif
    Endif
Return

6. Once the operation has been created, the operation must be called from the data class 'MYCLASS2' or from any other data class. Add a similar code to the following. This calls 'MYMETHOD' which is defined above.

##############################################
#  Data Class -  MYCLASS2                    #
##############################################

##############################################
#                METHODS                     #
##############################################
$METHODS
  Case CURPRO
    When ""
      Case ACTION
        When "AINSERT_AFTER" : Gosub AINSERT_AFTER
      Endcase
  Endcase

Return

#Action After insert
$AINSERT_AFTER

    # Declaration new instance of MYCLASS2 data class
    Local Instance MYCLASS Using C_MYCLASS2
    MYCLASS = NewInstance C_MYCLASS2 AllocGroup Null
    ASTATUS=fmet MYCLASS.MYMETHOD(KEYID,MYPARM1)
    If ASTATUS<>[V]CST_ATRUE
      ASTATUS = fmet THIS.ASETERROR ("", "Not updated.", [V]CST_AERROR)    
    Endif

    # Free instances
    FreeGroup MYCLASS
Return

7. Save your script.

8. Save and validate your data class.

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