Conditions

condition() is used to create a new condition function that itself returns a new condition.

conditions() retrieves all conditions based on search values. The parameters serve as filtering arguments.

Usage

condition(
  class,
  message = NULL,
  type = c("condition", "message", "warning", "error"),
  package = get_package(),
  exports = NULL,
  help = NULL,
  registry = package,
  register = !is.null(registry)
)

conditions(
  ...,
  class = NULL,
  type = NULL,
  package = NULL,
  registry = NULL,
  fun = NULL
)

cond(x)

cnd(condition)

conditions(x, ...) <- value

# S3 method for class '`function`'
conditions(x, append = FALSE, ...) <- value

# S3 method for class '`cnd::condition_progenitor`'
conditions(x, ...) <- value

Arguments

class: The name of the new class
message: The message to be displayed when the condition is called. When entered as a character vector, the message is collapsed into a single string. Use explicit line returns to generate new lines in output messages. When a function is used and a character vector returned, each element is treated as a new line.
type: The type of condition: error, warning, or message
package: The package to which the condition belongs
exports: The exported functions to be displayed when the condition is called
help: The help message to be displayed for the condition function
registry: The name of the registry to store the condition
register: Controls registration checks
...: Additional arguments passed to methods
fun: if a function is passed, then retrieves the "conditions" attribute
x: An object
condition: A condition_generator object
value: A condition
append: If TRUE, adds to the conditions attribute

Value

condition() a condition_generator object

conditions() a list of condition_generator objects

cond() A condition_generator object

cnd() is a wrapper for calling stop(), warning(), or message(); when condition is a type, an error is thrown, and likewise for the other types. When an error isn't thrown, the condition is returned, invisibly.

Details

Conditions

condition_generator

A condition_generator is an object (a special function) which can be used to create generate a new condition, based on specifications applied in condition(). These functions use ... to absorb extra arguments and contain a special .call parameter. By default, .call captures the parent call from where the condition_generator was created, but users may pass their own call to override this. See call. in conditionCall()

`condition()` conditions

Conditions are generated through the {cnd} package. The following conditions are associated with this function:

cnd:as_character_cnd_error/error

You cannot coerce a condition_generator object to a character. This may have occurred when trying to put a condition function through stop() or warning. Instead, call the function first, then pass the result to stop() or warning().

For example:

# Instead of this
stop(my_condition)

# Do this
stop(my_condition())

cnd:condition_message_generator/error

condition_generator objects are not conditions. You may have made this mistake:

x <- condition("my_condition")
conditionMessage(x)

Condition generators need to be called first before they can be used as conditions. Try this instead:

x <- condition("my_condition")
conditionMessage(x())

cnd:condition_overwrite/warning

cnd:invalid_condition/error

The class, exports, and help parameters must be a single character string. If you are passing a function, it must be a valid function.

cnd:invalid_condition_message/error

Conditions messages are displayed when invoked through conditionMessage(). You can set a static message by passing through a character vector, or a dynamic message by passing through a function. The function should return a character vector.

When message is not set, a default "there was an error" message is used.

cnd:match_arg/error

Mostly match.arg() but with a custom condition

cnd:no_package_exports/warning

The exports parameter requires a package

For more conditions, see: cnd-cnd-conditions

`cnd()` conditions