callHooks: Call hook functions by hook name

In R.utils: Various Programming Utilities

Call hook functions by hook name

Description

Call hook functions by hook name.

Usage

## Default S3 method:
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.

Author(s)

Henrik Bengtsson

See Also

Internally, after retrieving 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()


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# 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")

R.utils documentation built on Nov. 18, 2023, 1:09 a.m.