R: Produce the textual form of the signatures of available...

get_sig_text {Rdpack} | R Documentation

## Produce the textual form of the signatures of available methods for an S4 generic function

### Description

Produce the textual form of the signatures of available methods for an S4 generic function.

Here we find all methods for `show()` defined in package `"methods"` and print the first few of them:

    fn <- utils::help("show-methods", package = "methods")
    rdo <- utils:::.getHelpFile(fn)
    head(get_sig_text(rdo))
    ##: [1] "signature(object = \"ANY\")"
    ##: [2] "signature(object = \"MethodDefinition\")"
    ##: [3] "signature(object = \"MethodDefinitionWithTrace\")"
    ##: [4] "signature(object = \"MethodSelectionReport\")"
    ##: [5] "signature(object = \"MethodWithNext\")"
    ##: [6] "signature(object = \"MethodWithNextWithTrace\")"

### Usage

    get_sig_text(rdo, package = NULL)

### Arguments

`rdo` | an Rd object.
`package` | if of class "character", give only methods defined by `package`, otherwise give all methods.

### Details

Signatures are found using function `findMethodSignatures` from package "methods".

### Value

A character vector with one element for each method.

### Note

todo: It would be better to call promptMethods() to get the signatures but in version R-2.13.x I had trouble with argument ‘where’ (could not figure out how to use it to restrict to functions from a package; also, promptMethods() seemed to call the deprecated function getMethods()). Check how these things stand in current versions of R, there may be no problem any more (checked, in 2.14-0 it is the same).

### Author(s)

Georgi N. Boshnakov

### Examples

    require("stats4") # to ensure the presence of S4 methods from
                      # at least one package other than "methods"

    fn <- help("show-methods", package = "methods")
    rdo <- utils:::.getHelpFile(fn)

    # this will find all methods for "show" in currently loaded packages
    get_sig_text(rdo)

    # this will select only the ones from package "stats4"
    get_sig_text(rdo, package = "stats4")

    # this is also fine but need to choose
    # the appropriate element of "fn" if length(fn) > 1
    fn <- help("show-methods")

    # this finds nothing
    fn <- help("logLik-methods", package = "methods")

    # this does
    fn <- help("logLik-methods", package = "stats4")
    rdo <- utils:::.getHelpFile(fn)

    get_sig_text(rdo)
    get_sig_text(rdo, package = "stats4")

[Package Rdpack version 0.10-1 Index]