ITT Rule IDL Version 7.0 User Manual download pdf (Page 241)

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Chapter 9: Creating a File Reader 241

iTool Developer’s Guide Creating a New File Reader

Note

Any property registered with a call to the RegisterProperty method must be listed as

a keyword to the GetProperty method either of the visualization class or one of its

superclasses.

Note

A file reader need not register any properties at all, if the read operation is simple.

Many of the standard iTool image file readers work without registering any

properties.

See “IDLitReader::GetProperty” (IDL Reference Guide) for additional details.

Example GetProperty Method

PRO ExampleReader::GetProperty, _REF_EXTRA = _extra

IF (N_ELEMENTS(_extra) GT 0) THEN $

self->IDLitReader::GetProperty, _EXTRA = _extra

END

Discussion

The GetProperty method first defines the keywords it will accept. There must be a

keyword for each property of the file reader. Since the file reader we are creating has

no properties of its own, there are no keywords explicitly defined. The keyword

inheritance mechanism allows properties to be retrieved from the

ExampleReader

class’ superclasses without knowing the names of the properties.

Since our

ExampleReader class has no properties of its own, we simply call the

superclass’ GetProperty method, passing in all of the keywords stored in the

_extra

structure.

Creating a SetProperty Method

The file reader SetProperty method stores property values in the file reader object’s

instance data. It should set the specified property value, either by storing the value

directly in the visualization object’s instance data or by calling another class’

SetProperty method.

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ITT Rule IDL Version 7.0 User Manual Page 241

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