ITT Rule IDL Version 7.0 User Manual download pdf (Page 235)

Chapter 9: Creating a File Reader 235

iTool Developer’s Guide Creating a New File Reader

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

available to classes that subclass from IDLitReader.

Example Class Structure Definition

The following is the class structure definition for the ExampleReader file reader

class. This procedure should be the last procedure in a file named

examplereader__define.pro.

PRO ExampleReader__Define

struct = { ExampleReader, $

INHERITS IDLitReader $

}

END

Discussion

The purpose of the structure definition routine is to define a named IDL structure

with structure fields that will contain the visualization object instance data. The

structure name should be the same as the visualization’s class name — in this case,

ExampleReader.

Like many iTool file reader classes,

ExampleReader is created as a subclass of the

IDLitReader class. File reader classes that subclass from IDLitReader class inherit all

of the standard iTool file reader features, as described in “Subclassing from the

IDLitReader Class” on page 234.

The ExampleReader class has no instance data of its own. For a more complex

example, see “Example: TIFF File Reader” on page 248.

Creating an Init Method

The file reader class Init method handles any initialization required by the file reader

object, and should do the following:

• define the Init function method, using the keyword inheritance mechanism to

handle “extra” keywords

• call the Init methods of any superclasses, using the keyword inheritance

mechanism to pass “extra” keywords

• register any properties of your file reader, and set property attributes as

necessary

• perform other initialization steps as necessary

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ITT Rule IDL Version 7.0 User Manual Page 235