Exception {R.oo}

The Exception class to be thrown and caught

Description

Package: R.oo
Class Exception

Object
~~|
~~+--try-error
~~~~~~~|
~~~~~~~+--condition
~~~~~~~~~~~~|
~~~~~~~~~~~~+--error
~~~~~~~~~~~~~~~~~|
~~~~~~~~~~~~~~~~~+--simpleError
~~~~~~~~~~~~~~~~~~~~~~|
~~~~~~~~~~~~~~~~~~~~~~+--Exception

Directly known subclasses:
InternalErrorException, RccViolationException, RdocException

public static class Exception
extends simpleError

Creates an Exception that can be thrown and caught. The Exception class is the root class of all other Exception classes.

Usage

Exception(..., sep="", collapse=", ")

Arguments

...

One or several strings, which will be concatenated and contain informative message about the exception.

sep

The string to used for concatenating several strings.

collapse

The string to used collapse vectors together.

Fields and Methods

Methods:

	as.character	Gets a character string representing of the Exception.
	getCall	-
	getCalls	Gets the active calls saved when the exception was created.
	getLastException	Static method to get the last Exception thrown.
	getMessage	Gets the message of the Exception.
	getStackTrace	Gets the stack trace saved when the exception was created.
	getStackTraceString	Gets the stack trace as a string.
	getWhen	Gets the time when the Exception was created.
	print	Prints the Exception.
	printStackTrace	Prints the stack trace saved when the exception was created.
	throw	Throws an Exception that can be caught.

Methods inherited from error:
as.character, throw

Methods inherited from condition:
abort, as.character, conditionCall, conditionMessage, print

Methods inherited from Object:
$, $<-, [[, [[<-, as.character, attach, attachLocally, clearCache, clearLookupCache, clone, detach, equals, extend, finalize, getEnvironment, getFieldModifier, getFieldModifiers, getFields, getInstantiationTime, getStaticInstance, hasField, hashCode, ll, load, names, objectSize, print, save

Author(s)

Henrik Bengtsson

See Also

See also tryCatch() (and try()).

Examples

######################################################################
# 1. To catch a regular "error" exception thrown by e.g. stop().
######################################################################
x <- NA
y <- NA
tryCatch({
  x <- log(123)
  y <- log("a")
}, error = function(ex) {
  print(ex)
})
print(x)
print(y)



######################################################################
# 2. Always run a "final" expression regardless or error or not.
######################################################################
filename <- tempfile("R.methodsS3.example")
con <- file(filename)
tryCatch({
  open(con, "r")
}, error = function(ex) {
  cat("Could not open ", filename, " for reading.\n", sep="")
}, finally = {
  close(con)
  cat("The id of the connection is ",
       ifelse(is.null(con), "NULL", con), ".\n", sep="")
})


######################################################################
# 3. Creating your own Exception class
######################################################################
setConstructorS3("NegativeLogValueException", function(
  msg="Trying to calculate the logarithm of a negative value", value=NULL) {
  extend(Exception(msg=msg), "NegativeLogValueException",
    .value = value
  )
})

setMethodS3("as.character", "NegativeLogValueException", function(this, ...) {
  paste(as.character.Exception(this), ": ", getValue(this), sep="")
})

setMethodS3("getValue", "NegativeLogValueException", function(this, ...) {
  this$.value
})


mylog <- function(x, base=exp(1)) {
  if (x < 0)
    throw(NegativeLogValueException(value=x))
  else
    log(x, base=base)
}


# Note that the order of the catch list is important:
l <- NA
x <- 123
tryCatch({
  l <- mylog(x)
}, NegativeLogValueException = function(ex) {
  cat(as.character(ex), "\n")
}, "try-error" = function(ex) {
  cat("try-error: Could not calculate the logarithm of ", x, ".\n", sep="")
}, error = function(ex) {
  cat("error: Could not calculate the logarithm of ", x, ".\n", sep="")
})
cat("The logarithm of ", x, " is ", l, ".\n\n", sep="")