ITT Rule IDL Version 7.0 User Manual download pdf (Page 169)

Chapter 7: Creating an Operation 169

iTool Developer’s Guide Creating a New Generalized Operation

This convention is used in all operation classes included with IDL. ITT Visual

Information Solutions strongly suggests that you include similar checks in your own

class definition files.

Keywords to the Init Method

Properties of the operation class can be set in the Init method by specifying the

property names and values as IDL keyword-value pairs. In addition to any keywords

implemented directly in the Init method of the superclass on which you base your

class, the properties of the IDLitOperation class and the IDLitComponent class are

available to any operation class. See “IDLitOperation Properties” and

“IDLitComponent Properties” (IDL Reference Guide).

Note

Always use keyword inheritance (the _EXTRA keyword) to pass keyword

parameters through to the superclass. (See “Keyword Inheritance” (Chapter 5,

Application Programming) for details on IDL’s keyword inheritance mechanism.)

Standard Base Class

While you can create your new operation class from any existing operation class, in

many cases, operations that do not act directly on the data that underlies a

visualization will be subclassed directly from the base class IDLitOperation:

IF (self->IDLitOperation::Init(_EXTRA = _extra) EQ 0) $

THEN RETURN, 0

The IDLitOperation class provides the base iTool functionality used in all operation

classes created by ITT Visual Information Solutions. See “Subclassing from the

IDLitOperation Class” on page 166 for details.

Return Value

If all of the routines and methods used in the Init method execute successfully, it

should indicate successful initialization by returning 1. Other operation classes that

subclass from your operation class may check this return value, as your routine

should check the value returned by any superclass Init methods called.

Registering Properties

Operations can register properties with the iTool. Registered properties show up in

the property sheet interface, and can be modified interactively by users. The iTool

property interface is described in detail in Chapter 4, “Property Management”.

class:

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ITT Rule IDL Version 7.0 User Manual Page 169