Generic Function | Package: cg | ToC | DocOverview | CGDoc | RelNotes | FAQ | Index | PermutedIndex
| 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.

|  | ToC | DocOverview | CGDoc | RelNotes | FAQ | Index | PermutedIndex
| Allegro CL version 9.0 Unrevised from 8.2 to 9.0. 8.2 version