Search Environments for a Function

getFunction

Description

Searches environments for a function object, ignoring variables with non-function values.

Usage

getFunction(name, generic = TRUE, mustFind = TRUE,
            where = topenv(parent.frame()))
existsFunction(f, generic=TRUE, where=topenv(parent.frame()))

Arguments

name	a character string that specifies a variable name.
generic	This argument is currently ignored.
mustFind	a logical value. If TRUE (the default) and no function is found, the call generates an error. If FALSE and no function is found, the call returns NULL.
where	an environment that specifies where to start the search.
f	a character string that specifies a variable name.

Details

getFunction searches the specified environment, its parent environment, and so on, to find a variable with the specified name containing a function. If a variable with this name is found, but its value is not a function, it is ignored and the search continues.
existsFunction performs the same search, returning TRUE if a suitable function is found. If a suitable function is not found, it returns FALSE.

Value

getFunction	returns a function object; otherwise it returns NULL if the function is not found and mustFind is FALSE.
existsFunction	returns TRUE if a suitable function is found; otherwise it returns FALSE.

See Also

get, is.function, parent.env.

Examples

# test mustFind argument
getFunction("nonExistantFunction", mustFind=FALSE) # returns NULL
# find function in global environment
xx <- function(x) x+1
existsFunction("xx")
identical(getFunction("xx")(1),2)
e1 <- new.env()
e2 <- new.env(parent=e1)
assign("xx", function(x)x+10, envir=e1)
assign("xx", 34, envir=e2)
# search for "xx" in e2 (ignoring non-function),
# then e1 (finding function)
identical(getFunction("xx", where=e2)(1),11)
existsFunction("xx", where=e2)

Package methods version 6.0.0-69
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