ITT Rule IDL Version 7.0 Uživatelský manuál stáhnout pdf (Strana 178)

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178 Chapter 7: Creating an Operation

Creating a New Generalized Operation iTool Developer’s Guide

Creating an UndoOperation Method

The operation class UndoOperation method is called when the user undoes the

operation by selecting “Undo” from a menu or toolbar.

Example UndoOperation Method

The following example code shows a very simple UndoOperation method for the

ExampleOp operation:

FUNCTION ExampleOp::UndoOperation, oCommandSet

; Retrieve the IDLitCommand objects stored in the

; command set object.

oCmds = oCommandSet->Get(/ALL, COUNT = nObjs)

; Get a reference to the iTool object.

oTool = self->GetTool()

; Loop through the IDLitCommand objects and restore the

; original values.

FOR i = 0, nObjs-1 DO BEGIN

oCmds[i]->GetProperty, TARGET_IDENTIFIER = idTarget

oTarget = oTool->GetByIdentifier(idTarget)

; Get the old value

IF (oCmds[i]->GetItem('OLD_STYLE', styleIndex) EQ 1) THEN $

oTarget->SetProperty, STYLE = styleIndex

ENDFOR

RETURN, 1

END

Discussion

The UndoOperation method does the following things:

1. Retrieves an array of IDLitCommand objects from the supplied

IDLitCommandSet object

2. Gets a reference to the iTool object.

3. For each command object, retrieve the identifier string for the target object.

Use the identifier string to retrieve a reference to the target object itself.

4. Retrieve the OLD_STYLE item from the command object and use its value to

set the STYLE property on the target object.

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