| methods {utils} | R Documentation |
List all available methods for a S3 and S4 generic function, or all methods for an S3 or S4 class.
methods(generic.function, class) .S3methods(generic.function, class, envir=parent.frame()) ## S3 method for class 'MethodsFunction' print(x, byclass = attr(x, "byclass"), ...)
generic.function |
a generic function, or a character string naming a generic function. |
class |
a symbol or character string naming a class: only used if
|
envir |
the environment in which to look for the definition of the generic function, when the generic function is passed as a character string. |
x |
typically the result of |
byclass |
an optional |
... |
potentially further arguments passed to and from methods; unused currently. |
methods() finds S3 and S4 methods associated with either the
generic.function or class argument. Methods are found in
all packages on the current search() path. .S3methods()
finds only S3 methods, .S4methods() finds only only S4 methods.
When invoked with the generic.function argument, the
"byclass" attribute (see Details) is FALSE, and the
print method by default displays the signatures (full names) of
S3 and S4 methods. S3 methods are printed by pasting the generic
function and class together, separated by a ‘.’, as
generic.class. The S3 method name is followed by an asterisk
* if the method definition is not exported from the package
namespace in which the method is defined. S4 method signatures are
printed as generic,class-method; S4 allows for multiple
dispatch, so there may be several classes in the signature
generic,A,B-method.
When invoked with the class argument, "byclass" is
TRUE, and the print method by default displays the names
of the generic functions associated with the class, generic.
The source code for all functions is available. For S3 functions
exported from the namespace, enter the method at the command line as
generic.class. For S3 functions not exported from the
namespace, see getAnywhere or getS3method. For S4
methods, see getMethod.
Help is available for each method, in addition to each generic. For
interactive help, use the documentation shortcut ? with the
name of the generic and tab completion, ?"generic<tab>" to
select the method for which help is desired.
The S3 functions listed are those which are named like methods and may not actually be methods (known exceptions are discarded in the code).
An object of class "MethodsFunction", a character vector of
method names with "byclass" and "info" attributes. The
"byclass" attribute is a logical indicating if
the results were obtained with argument class
defined. The "info" attribute is a data frame with columns:
character vector of the names of the generic.
logical(), is the method exported from the namespace of the package in which it is defined?
logical(), true when the method is an S4 method.
a factor, the location or package name
where the method was found.
The original methods function was written by Martin Maechler.
Chambers, J. M. (1992) Classes and methods: object-oriented programming in S. Appendix A of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.
S3Methods, class, getS3method.
For S4, getMethod, showMethods,
Introduction or Methods_Details.
require(stats)
methods(summary)
methods(class = "aov") # S3 class
## The same, with more details and more difficult to read:
print(methods(class = "aov"), byclass=FALSE)
methods("[[") # uses C-internal dispatching
methods("$")
methods("$<-") # replacement function
methods("+") # binary operator
methods("Math") # group generic
require(graphics)
methods("axis") # looks like a generic, but is not
if(require(Matrix)) {
print(methods(class = "Matrix")) # S4 class
m <- methods("dim") # S3 and S4 methods
print(m)
print(attr(m, "info")) # more extensive information
## --> help(showMethods) for related examples
}