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Allegro CL version 9.0
Unrevised from 8.2 to 9.0.
8.2 version

property-value

Arguments: object property-or-name

Returns the current value of a specified property of object. property-or-name should be either a property object or the symbol that names the property. When property-or-name is a property object, it should be one that was returned by calling properties on the same object that is now being passed to property-value. Passing the property object is more efficient than passing the property name.

To retrieve the values of particular properties when the names of the property-reader functions are known, it is more efficient to call the reader functions directly. But calling property-value may be useful for meta-level uses such as finding the values of all of the properties of an object. For example, the following function returns a list of the names and values of all of the properties of an object.

(defun list-properties (object)
  (mapcar #'(lambda (property)
              (list (name property)
                    (property-value object property)))
    (properties object)))

If property-or-name is a symbol but no property of object is found by that name, then an error is signaled. Otherwise the property-reader of the property is called, and the value that it returns is returned. If an error occurs in the call to the property-reader function, the error is trapped and the keyword :property-read-error is returned.

See defproperties for information on defining properties on any type of object.


Copyright (c) 1998-2019, Franz Inc. Oakland, CA., USA. All rights reserved.
This page was not revised from the 8.2 page.
Created 2012.5.30.

ToCDocOverviewCGDocRelNotesFAQIndexPermutedIndex
Allegro CL version 9.0
Unrevised from 8.2 to 9.0.
8.2 version