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Create a condition object

Source: R/cnd.R
cnd.Rd

These constructors create subclassed conditions, the objects that power the error, warning, and message system in R.

  • cnd() creates bare conditions that only inherit from condition.

  • Conditions created with error_cnd(), warning_cnd(), and message_cnd() inherit from "error", "warning", or "message".

  • error_cnd() creates subclassed errors. See "rlang_error".

Use cnd_signal() to emit the relevant signal for a particular condition class.

Usage

cnd(class, ..., message = "", call = NULL, use_cli_format = NULL)

error_cnd(
  class = NULL,
  ...,
  message = "",
  call = NULL,
  trace = NULL,
  parent = NULL,
  use_cli_format = NULL
)

warning_cnd(
  class = NULL,
  ...,
  message = "",
  call = NULL,
  use_cli_format = NULL
)

message_cnd(
  class = NULL,
  ...,
  message = "",
  call = NULL,
  use_cli_format = NULL
)

Arguments

class

The condition subclass.

...

<dynamic> Named data fields stored inside the condition object.

message

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

call

A function call to be included in the error message. If an execution environment of a running function, the corresponding function call is retrieved.

use_cli_format

Whether to use the cli package to format message. See local_use_cli().

trace

A trace object created by trace_back().

parent

A parent condition object.

See also

cnd_signal(), try_fetch().

Examples

# Create a condition inheriting only from the S3 class "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 transfers control
# to the handler
with_handlers(cnd_signal(cnd), foo = function(c) "caught!")
#> Warning: `with_handlers()` is deprecated as of rlang 1.0.0.
#> ℹ Please use `tryCatch()`, `withCallingHandlers()`, or `try_fetch()`.
#> This warning is displayed once every 8 hours.
#> [1] "caught!"
tryCatch(cnd_signal(cnd), foo = function(c) "caught!")
#> [1] "caught!"