objectclass

#objectclass

##Syntax objectclass ( pointerExpn )

##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.

##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

##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:

is not allowed.

    var p : ^objectclass (q)