R doesn’t come with a built-in constructor function for conditions, but we can easily add one.
(Advanced R, by Hadley Wickham)
Actually, there is simpleCondition()
, simpleError()
and the like,
but they don't allow specifying an additional class.
The functions in this package allow it:
library(condition) cond <- new_error("Something went wrong", class = "oops") cond is.error(cond)
Everything is powered by an R6 generator class that creates condition class objects:
Condition Error
These condition objects can be used instead the plain functions:
Error$new("Plain error")
If a custom condition is used more than once, it is a good idea to formalize it:
Oops <- ConditionClass$new("oops", Error) oops <- Oops$new("Something went wrong") oops Oops$is(oops)
A custom condition object inherits from its base:
Error$is(oops)
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