Extend the RunBase class

When you extend functionality of the application suite, you will encounter classes that extend the RunBase class. This article shows how a RunBase class can be augmented end to end.

For example, you want to extend the SysUserLogCleanup class. Out of the box, this class can delete records from the SysUserLog table. However, you want to archive these records to a different table before they are deleted.

The SysUserLogCleanup class is a RunBase class. The RunBase class has a dialog box, where the user is prompted for parameters before the class is run. For this example, we will add a toggle button control to the dialog box, get the value of the control, act on the value in the run method, and make sure that the value is serialized via the pack and unpack methods. Serialization helps guarantee that the user’s last selection is presented again if the dialog box is reopened. It also helps guarantee that the settings are applied if the class is run in the background.

To avoid collisions with other eventual extensions, we followed these best practices:

• Prefix members and methods. In the example, the prefix “my” is used. This practice is important, because it helps prevent name clashes with other extensions and future versions of the augmented class.

• Use RunBase.packExtension() and RunBase.unpackExtension(). These methods provide serialization in a nonintrusive manner. They enable serialization of multiple extensions of the same class. The methods are available starting in Platform Update 5.

The following example shows how to implement this scenario.

[ExtensionOf(classStr(SysUserLogCleanup))]
final class MySysUserLogCleanup_Extension
{
    // static members
    static private SysUserLogCleanup myRunningInstance;

    // Extending class state...
    private boolean myArchive;
    private DialogField myDialogArchive;
    #define.CurrentVersion(1)
    #localmacro.CurrentList
        myArchive
    #endmacro

    public Object dialog()
    {
        Dialog dialog = next dialog();

        myDialogArchive = dialog.addField(extendedtypestr(NoYesId), "Archive");
        myDialogArchive.value(myArchive);

        return dialog;
    }

    public boolean getFromDialog()
    {
        boolean result = next getFromDialog();
        myArchive = myDialogArchive.value();
        return result;
    }
    
    public void initParmDefault()
    {
        next initParmDefault();
        myArchive = true;
    }    

    public void run()
    {
        try
        {
            myRunningInstance = this;
            next run();
        }
        finally
        {
            myRunningInstance = null;
        }
    }

    public container pack()
    {
        container packedClass = next pack();
        return SysPackExtensions::appendExtension(packedClass, classStr(MySysUserLogCleanup_Extension), this.myPack());
    }

    private boolean myUnpack(container packedClass)
    {
        Integer version = RunBase::getVersion(packedClass);
        switch (version)
        {
            case #CurrentVersion:
                [version, #currentList] = packedClass;
                break;
            default:
                return false;
        }
        return true;
    }

    private container myPack()
    {
        return [#CurrentVersion, #CurrentList];
    }

    public boolean unpack(container _packedClass)
    {
        boolean result = next unpack(_packedClass);

        if (result)
        {
            container myState = SysPackExtensions::findExtension(_packedClass, classStr(MySysUserLogCleanup_Extension));
            //Also unpack the extension
            if (!this.myUnpack(myState))
            {
                result = false;
            }
        }

        return result;
    }
    
    private void myArchiveUserLog(SysUserLog _userLog)
    {
        if (myArchive)
        {
            //...
        }
    }

    // Wire up event handler for deletion of the record
    [DataEventHandler(tableStr(SysUserLog), DataEventType::Deleting)]
    static public void SysUserLog_onDeleting(Common _sender, DataEventArgs _e)
    {
        if (myRunningInstance)
        {
            myRunningInstance.myArchiveUserLog(_sender as SysUserLog);
        }
    }
}