isS3method {utils} | R Documentation

## Is 'method' the Name of an S3 Method?

### Description

Checks if `method` is the name of a valid / registered S3 method. Alternatively, when `f` and `class` are specified, it is checked if `f` is the name of an S3 generic function and `paste(f, class, sep=".")` is a valid S3 method.

### Usage

    isS3method(method, f, class, envir = parent.frame())

### Arguments

`method` | a character string, typically of the form `"<fn>.<class>"`. If omitted, `f` and `class` have to be specified instead.
`f` | optional character string, typically specifying an S3 generic function. Used, when `method` is not specified.
`class` | optional character string, typically specifying an S3 class name. Used, when `method` is not specified.
`envir` | the `environment` in which the method and its generic are searched first, as in `getS3method()`.

### Value

`logical` `TRUE` or `FALSE`

### See Also

`methods`, `getS3method`.

### Examples

    isS3method("t")           # FALSE - it is an S3 generic
    isS3method("t.default")   # TRUE
    isS3method("t.ts")        # TRUE
    isS3method("t.test")      # FALSE
    isS3method("t.data.frame")# TRUE
    isS3method("t.lm")        # FALSE - not existing
    isS3method("t.foo.bar")   # FALSE - not existing

    ## S3 methods with "4 parts" in their name:
    ff <- c("as.list", "as.matrix", "is.na", "row.names", "row.names<-")
    for(m in ff) if(isS3method(m)) stop("wrongly declared an S3 method: ", m)
    (m4 <- paste(ff, "data.frame", sep="."))
    for(m in m4) if(!isS3method(m)) stop("not an S3 method: ", m)

[Package utils version 3.4.2 Index]