cnd {rlang} | R Documentation |
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(.type = NULL, ..., .msg = NULL) error_cnd(.type = NULL, ..., .msg = NULL) warning_cnd(.type = NULL, ..., .msg = NULL) message_cnd(.type = NULL, ..., .msg = NULL)
.type |
The condition subclass. |
... |
Named data fields stored inside the condition object. These dots are evaluated with explicit splicing. |
.msg |
A default message to inform the user about the condition when it is signalled. |
cnd()
creates objects inheriting from condition
. Conditions
created with error_cnd()
, warning_cnd()
and message_cnd()
inherit from error
, warning
or message
.
cnd_signal()
, with_handlers()
.
# Create a condition inheriting from the s3 type "foo": cnd <- cnd("foo") # Signal the condition to potential handlers. This has no effect if no # handler is registered to deal with conditions of type "foo": cnd_signal(cnd) # If a relevant handler is on the current evaluation stack, it will be # called by cnd_signal(): with_handlers(cnd_signal(cnd), foo = exiting(function(c) "caught!")) # Handlers can be thrown or executed inplace. See with_handlers() # documentation for more on this. # Note that merely signalling a condition inheriting of "error" is # not sufficient to stop a program: cnd_signal(error_cnd("my_error")) # you need to use stop() to signal a critical condition that should # terminate the program if not handled: # stop(error_cnd("my_error"))