Syntax

find-method generic-function method-qualifiers specializers &optional errorp
⇒ method

Method Signatures

find-method (generic-function standard-generic-function) method-qualifiers specializers &optional errorp

Arguments and Values

Description

The generic function find-method takes a generic function and returns the method object that agrees on qualifiers and parameter specializers with the method-qualifiers and specializers arguments of find-method. Method-qualifiers contains the method qualifiers for the method. The order of the method qualifiers is significant. For a definition of agreement in this context, see Agreement on Parameter Specializers and Qualifiers.

The specializers argument contains the parameter specializers for the method. It must correspond in length to the number of required arguments of the generic function, or an error is signaled. This means that to obtain the default method on a given generic-function, a list whose elements are the class t must be given.

If there is no such method and errorp is true, find-method signals an error. If there is no such method and errorp is false, find-method returns nil.

Examples

 (defmethod some-operation ((a integer) (b float)) (list a b))
⇒  #<STANDARD-METHOD SOME-OPERATION (INTEGER FLOAT) 26723357>
 (find-method #'some-operation '() (mapcar #'find-class '(integer float)))
⇒  #<STANDARD-METHOD SOME-OPERATION (INTEGER FLOAT) 26723357>
 (find-method #'some-operation '() (mapcar #'find-class '(integer integer)))
 |>  Error: No matching method
 (find-method #'some-operation '() (mapcar #'find-class '(integer integer)) nil)
⇒  NIL

Affected By

add-method, defclass, defgeneric, defmethod

Exceptional Situations

If the specializers argument does not correspond in length to the number of required arguments of the generic-function, an an error of type error is signaled.

If there is no such method and errorp is true, find-method signals an error of type error.

See Also

Agreement on Parameter Specializers and Qualifiers

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