| GenericFunctions {methods} | R Documentation |
The functions documented here manage collections of methods associated with a generic function, as well as providing information about the generic functions themselves.
isGeneric(f, where, fdef, getName = FALSE)
isGroup(f, where, fdef)
removeGeneric(f, where)
standardGeneric(f)
dumpMethod(f, signature, file, where, def)
existsFunction(f, generic = TRUE, where)
findFunction(f, generic=TRUE)
dumpMethods(f, file, signature, methods, where)
signature(...)
removeMethods(f, where)
setReplaceMethod(f, ...)
getGenerics(where, searchForm = FALSE)
allGenerics(where, searchForm = FALSE)
callGeneric(...)
f |
The character string naming the function. |
where |
Where on the search list of attached packages to look for functions or methods. By default, use the whole search list to find the relevant object(s). |
signature |
The class signature of the relevant method. A
signature is a named or unnamed vector of character strings. If
named, the names must be formal argument names for the generic
function. If |
file |
The file on which to dump method definitions. |
def |
The function object defining the method; if omitted, the current method definition corresponding to the signature. |
... |
Named or unnamed arguments to form a signature. |
generic |
In testing or finding functions, should generic
functions be included. Supply as |
fdef |
Optional, the generic function definition. Usually omitted in calls to |
getName |
If |
methods |
The methods object containing the methods to be dumped. By default,
the methods defined for this generic (optionally on the specified
|
searchForm |
In |
isGeneric:Is there a function named f, and if so, is it a generic?
The getName argument allows a function to find the name
from a function definition. If it is TRUE then the name of
the generic is returned, or FALSE if this is not a generic
function definition.
The behavior of isGeneric and getGeneric for
primitive functions is slightly different. These functions don't
exist as formal function objects (for efficiency and historical
reasons), regardless of whether methods have been defined for
them. A call to isGeneric tells you whether methods have
been defined for this primitive function, anywhere in the
current search list, or in the specified position where. In contrast,
a call to getGeneric will return what the generic
for that function would be, even if no methods have been currently
defined for it.
removeGeneric, removeMethods:Remove the all the methods for the generic function of this
name. In addition, removeGeneric removes the function
itself; removeMethods restores the non-generic function
which was the default method. If there was no default method,
removeMethods leaves a generic function with no methods.
standardGeneric:Dispatches a method from the current function call for the generic
function f. It is an error to call
standardGeneric anywhere except in the body of the
corresponding generic function.
getMethods:The list of methods for the specified generic.
dumpMethod:Dump the method for this generic function and signature.
existsFunction:Is there a function of this name. If generic is
FALSE, generic functions are not counted.
findFunction:return all the elements of the search list on which a function
definition for name exists.
NOTE: Use this rather than find with
mode="function", which is not as meaningful, and has a few
subtle bugs from its use of regular expressions.
selectMethod:Returns the method (a function) that R would use to evaluate a call to this generic, with arguments corresponding to the specified signature.
f = the name of the generic function, signature is
the signature of classes to match to the arguments of f.
dumpMethods:Dump all the methods for this generic.
signature:Returns a named list of classes to be matched to arguments of a generic function.
getGenerics: Returns the names of the generic
functions that have methods defined on where; this
argument can be an environment or an index into the search
list. By default, the whole search list is used.
The methods definitions are stored with
package qualifiers; for example, methods for function
"initialize" might refer to two different functions
of that name, on different packages. The package names
corresponding to the method list object are contained in the
slot package of the returned object. The form of
the returned name can be plain (e.g., "base"), or in
the form used in the search list ("package:base")
according to the value of searchForm
callGeneric:In the body of a method, this function will make a call to the
current generic function. If no arguments are passed to
callGeneric, the arguments to the current call are passed
down; otherwise, the arguments are interpreted as in a call to the
generic function.
setGeneric:If there is already a non-generic function of this name, it will
be used to define the generic unless def is supplied, and
the current function will become the default method for the
generic.
If def is supplied, this defines the generic function, and
no default method will exist (often a good feature, if the
function should only be available for a meaningful subset of all
objects).
Arguments group and valueClass are retained for
consistency with S-Plus, but are currently not used.
isGeneric:If the fdef argument is supplied, take this as the
definition of the generic, and test whether it is really a
generic, with f as the name of the generic. (This argument
is not available in S-Plus.)
removeGeneric:If where supplied, just remove the version on this element
of the search list; otherwise, removes the first version
encountered.
standardGeneric:Generic functions should usually have a call to
standardGeneric as their entire body. They can, however,
do any other computations as well.
The usual setGeneric (directly or through calling
setMethod) creates a function with a call to
standardGeneric.
getMethods:If the function is not a generic function, returns NULL.
The f argument can be either the character string name of
the generic or the object itself.
The where argument optionally says where to look for the
function, if f is given as the name.
dumpMethod:The resulting source file will recreate the method.
findFunction:If generic is FALSE, ignore generic functions.
selectMethod:The vector of strings for the classes can be named or not. If
named, the names must match formal argument names of f. If
not named, the signature is assumed to apply to the arguments of
f in order.
If mustFind is TRUE, an error results if there is no
method (or no unique method) corresponding to this signature.
Otherwise may return NULL or a MethodsList object.
dumpMethods:If signature is supplied only the methods matching this
initial signature are dumped. (This feature is not found in
S-Plus: don't use it if you want compatibility.)
signature:The advantage of using signature is to provide a check on
which arguments you meant, as well as clearer documentation in
your method specification. In addition, signature checks
that each of the elements is a single character string.
removeMethods:Returns TRUE if f was a generic function,
FALSE (silently) otherwise.
If there is a default method, the function will be re-assigned as
a simple function with this definition.
Otherwise, the generic function remains but with no methods (so
any call to it will generate an error). In either case, a
following call to setMethod will consistently
re-establish the same generic function as before.
The R package methods implements, with a few exceptions, the
programming interface for classes
and methods in the book Programming with Data (John
M. Chambers, Springer, 1998), in particular sections 1.6, 2.7, 2.8,
and chapters 7 and 8.
While the programming interface for the methods package follows the reference, the R software is an original implementation, so details in the reference that reflect the S4 implementation may appear differently in R. Also, there are extensions to the programming interface developed more recently than the reference. For a discussion of details and ongoing development, see the web page http://developer.r-project.org/methodsPackage.html and the pointers from that page.
setGeneric,
setClass,
showMethods