R: List Methods for S3 Generic Functions or Classes

methods {utils} | R Documentation

## List Methods for S3 Generic Functions or Classes

### Description

List all available methods for an S3 generic function, or all methods for a class.

### Usage

    methods(generic.function, class)

### Arguments

`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 `generic.function` is not supplied.

### Details

Function `methods` can be used to find out about the methods for a particular generic function or class. The functions listed are those which are named like methods and may not actually be methods (known exceptions are discarded in the code). Note that the listed methods may not be user-visible objects, but often help will be available for them.

If `class` is used, we check that a matching generic can be found for each user-visible object named. If `generic.function` is given, there is a warning if it appears not to be a generic function. (The check for being generic used can be fooled.)

### Value

An object of class `"MethodsFunction"`, a character vector of function names with an `"info"` attribute. There is a `print` method which marks with an asterisk any methods which are not visible: such functions can be examined by `getS3method` or `getAnywhere`.

The `"info"` attribute is a data frame, currently with a logical column, `visible` and a factor column `from` (indicating where the methods were found).

### Note

This scheme is called S3 (S version 3). For new projects, it is recommended to use the more flexible and robust S4 scheme provided in the methods package. Functions can have both S3 and S4 methods, and function `showMethods` will list the S4 methods (possibly none).

The original `methods` function was written by Martin Maechler.

### References

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.

### See Also

`S3Methods`, `class`, `getS3method`.

For S4, `showMethods`, `Methods`.

### Examples

    require(stats)

    methods(summary)
    methods(class = "aov")
    methods("[[")    # uses C-internal dispatching
    methods("$")
    methods("$<-")   # replacement function
    methods("+")     # binary operator
    methods("Math")  # group generic
    require(graphics)
    methods("axis")  # looks like it has methods, but not generic
    ## Not run:
    methods(print)   # over 100

    ## End(Not run)
    ## --> help(showMethods) for related examples

[Package utils version 3.1.2 Index]