How to change the properties of one data class from another data class using an operation

This ‘How-to’ provides information on how to use an operation to change the properties (fields) of one data class from a different data 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 a simple script to a given data class (MYCLASS1) to create on (MYCLASS1) an operation which is called from a different data class (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 automatically generate 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 PROP1.

$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 MYPARM1 are passed and used in this operation

$MYMETHOD

    # Use standard method CRUD to read MYCLASS1
    ASTATUS=fmet THIS.AREAD(KEY1) 
    If ASTATUS<>[V]CST_AOK 
      ARET_VALUE= CST_AFALSE
      Return
    Endif

    # Update PROP1 using MYPARM1
    THIS.PROP1 = MYPARM1

    # Update MYCLASS1
    ASTATUS=fmet THIS.AUPDATE
    If ASTATUS<>[V]CST_AOK # check status after update
       ARET_VALUE= CST_AFALSE
      Return

    Endif

ARET_VALUE= CST_ATRUE 
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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