Sends an error-level message to the logging system.
- iOS 10.0+
- macOS 10.12+
- tvOS 10.0+
- watchOS 3.0+
A constant string or format string that produces a human-readable log message. See Formatting Log Messages.
Error-level messages sent by this function are always saved in the data store. They remain there until the storage quota is exceeded, at which point, the oldest messages are purged. Error-level messages are intended for reporting process-level errors. If an activity object exists, logging at this level captures information for the entire process chain.
Calling this function is equivalent to calling the
os function and specifying a log type of
OS. Note that lengthy log messages may be truncated when stored by the logging system.