R.utils (version 2.3.0)

callHooks: Call hook functions by hook name

Description

Call hook functions by hook name.

Usage

"callHooks"(hookName, ..., removeCalledHooks=FALSE)

Arguments

hookName

A character string of the hook name.

...

Argument passed to each hook function.

removeCalledHooks

If TRUE, called hook functions are removed, otherwise not.

Value

Returns (invisibly) whatever callHooks.list() returns.

See Also

Internally, after retriving hook functions, callHooks.list() is called.

Examples

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# Example 1
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# First, clean up if called more than once
setHook("myFunction.onEnter", NULL, action="replace")
setHook("myFunction.onExit", NULL, action="replace")

runConference <- function(...) {
  callHooks("myFunction.onEnter")
  cat("Speaker A: Hello there...\n")
  callHooks("myFunction.onExit")
}

setHook("myFunction.onEnter", function(...) {
  cat("Chair: Welcome to our conference.\n")
})

setHook("myFunction.onEnter", function(...) {
  cat("Chair: Please welcome Speaker A!\n")
})

setHook("myFunction.onExit", function(...) {
  cat("Chair: Please thanks Speaker A!\n")
})

runConference()


# - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Example 2
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setHook("randomNumber", NULL, action="replace")
setHook("randomNumber", rnorm)      # By function
setHook("randomNumber", "rexp")     # By name
setHook("randomNumber", "runiff")   # Non-existing name
setHook("randomNumber", .GlobalEnv) # Not a function

res <- callHooks("randomNumber", n=1)
str(res)
cat("Number of hooks: ", length(res), "\n");
isErroneous <- unlist(lapply(res, FUN=function(x) !is.null(x$exception)));
cat("Erroneous hooks: ", sum(isErroneous), "\n");