ITT Rule IDL Version 7.0 User Manual download pdf (Page 207)

Chapter 8: Creating a Manipulator 207

iTool Developer’s Guide Creating a New Manipulator

Creating the Manipulator Class Structure Definition

When any IDL object is created, IDL looks for an IDL class structure definition that

specifies the instance data fields needed by an instance of the object, along with the

data types of those fields. The object class structure must be defined before any

objects of the type are created. In practice, when the IDL OBJ_NEW function

attempts to create an instance of a specified object class, it executes a procedure

named

ObjectClass

__define (where ObjectClass is the name of the object),

which is expected to define an IDL structure variable with the correct name and

structure fields. For additional information on how IDL creates object instances, see

“The Object Lifecycle” (Chapter 13, Object Programming).

Note

The class structure definition is generally the last routine in the

.pro file that

defines an object class.

Subclassing From the IDLitManipulator Class

The IDLitManipulator class is the base class for all iTool manipulators. In almost all

cases, new manipulators will be subclassed either from the IDLitManipulator class or

from a class that is a subclass of IDLitManipulator.

Note

If you are implementing a number of manipulators that provide similar

functionality, and you want the user to choose one out of the group of items, you

may want to create a manipulator container. See “Manipulators and Manipulator

Containers” on page 194 for an introduction to these objects.

See “IDLitManipulator” (IDL Reference Guide) for details on the methods and

properties available to classes that subclass from IDLitManipulator.

Example Class Structure Definition

The following is the class structure definition for the ExampleManip operation class.

This procedure should be the last procedure in a file named

examplemanip__define.pro.

; Class Definition.

PRO ExampleManip__define

; Define the MyManipulator class structure, which inherits the

; IDLitManipulator class.

struct = { ExampleManip, $

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ITT Rule IDL Version 7.0 User Manual Page 207