toscutil (version 2.8.0)

caller: Get Name of Calling Function

Description

Returns the name of a calling function as string, i.e. if function g calls function f and function f calls caller(2), then string "g" is returned.

Usage

caller(n = 1)

Value

Name of the calling function

Arguments

n

How many frames to go up in the call stack

Details

Be careful when using caller(n) as input to other functions. Due to R's non-standard-evaluation (NES) mechanism it is possible that the function is not executed directly by that function but instead passed on to other functions, i.e. the correct number of frames to go up cannot be predicted a priori. Solutions are to evaluate the function first, store the result in a variable and then pass the variable to the function or to just try out the required number of frames to go up in an interactive session. For further examples see section Examples.

Examples

# Here we want to return a list of all variables created inside a function
f <- function(a = 1, b = 2) {
    x <- 3
    y <- 4
    return(locals(without = formalArgs(caller(4))))
    # We need to go 4 frames up, to catch the formalArgs of `f`, because the
    # `caller(4)` argument is not evaluated directly be `formalArgs`.
}
f() # returns either list(x = 3, y = 4) or list(y = 4, x = 3)

# The same result could have been achieved as follows
g <- function(a = 1, b = 2) {
    x <- 3
    y <- 4
    func <- caller(1)
    return(locals(without = c("func", formalArgs(func))))
}
g() # returns either list(x = 3, y = 4) or list(y = 4, x = 3)