| objectclass | of a pointer |
| Syntax | objectclass ( pointerExpn )
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| Description | The objectclass attribute is used to find the class of an object located by a pointer. The pointerExpn must be an expression that is a pointer to a class.
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| Example | See class for an example of classes and inheritance, in which a class called TextFile is inherited by a class called Device. The Device class adds a new exported procedure called ioCtl. In the present example, objectclass is used to test to make sure that the textFilePtr currently locates an object that was created as a Device (or as a descendant of Device). The notation Device(textFilePtr) converts the pointer to be a pointer to a Device so that ioCtl can be called.
var textFilePtr : ^ TextFile
…
if objectclass ( textFilePtr ) >= Device then
% Can safely treat object as a Device
Device ( textFilePtr ) . ioCtl
…
end if
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| Details | This example uses the class comparison operator >= which means "is a descendant of". See class. You can only use objectclass in class comparisons. In particular, objectclass cannot be used to declare pointers. For example, this:
var p : ^objectclass (q)is not allowed.
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