These constructors make it easy to create subclassed conditions. Conditions are objects that power the error system in R. They can also be used for passing messages to pre-established handlers.

cnd(.subclass, ..., message = "")

error_cnd(.subclass = NULL, ..., message = "", trace = NULL,
  parent = NULL)

warning_cnd(.subclass = NULL, ..., message = "")

message_cnd(.subclass = NULL, ..., message = "")

Arguments

.subclass

The condition subclass.

...

Named data fields stored inside the condition object. These dots are evaluated with explicit splicing.

message

A default message to inform the user about the condition when it is signalled.

trace

A trace object created by trace_back().

parent

A parent condition object created by abort().

Details

cnd() creates objects inheriting from condition. Conditions created with error_cnd(), warning_cnd() and message_cnd() inherit from error, warning or message.

Lifecycle

The .type and .msg arguments have been renamed to .subclass and message. They are defunct as of rlang 0.3.0.

See also

Examples

# Create a condition inheriting from the s3 type "foo": cnd <- cnd("foo") # Signal the condition to potential handlers. Since this is a bare # condition the signal has no effect if no handlers are set up: cnd_signal(cnd) # When a relevant handler is set up, the signal causes the handler # to be called: with_handlers(cnd_signal(cnd), foo = exiting(function(c) "caught!"))
#> [1] "caught!"
# Handlers can be thrown or executed inplace. See with_handlers() # documentation for more on this. # Signalling an error condition aborts the current computation: err <- error_cnd("foo", message = "I am an error") try(cnd_signal(err))