SwiftLogger

Dependency free Logger API for Swift.

Motivation

Beside obvious benefit for unit testing (see NullLogger), having loose coupling to a logging framework makes it easy to log messages into multiple logging systems at once (see AgregateLogger).

Usage

Logger protocol provides simple interface utilizing log levels defined by The Syslog Protocol - RFC5424.

logger.log("message", level: .emergency)
logger.log("message", level: .alert)
logger.log("message", level: .critical)
logger.log("message", level: .error)
logger.log("message", level: .warning)
logger.log("message", level: .notice)
logger.log("message", level: .informational)
logger.log("message", level: .debug)

Log calls capture time, file name, method name and line number automatically. This way it is possible to compose log messages similar to the one presented below.

2018-08-31 18:29:34.748 <crit> SwiftFile:75 method() message

Integration with logger frameworks

You need to provide implementation for one method.

final class CustomLogger: Logger {
    
    public func log(time: Date, level: LogLevel, location: String, message: @autoclosure () -> String) {
        /// compose message and forward it to a logging framework
    }
}

Provided loggers

ConsoleLogger writes messages into the standard output.

NullLogger ignores all messages with the intention to minimize observer effect. Useful for unit testing.

DiskLogger writes messages into the file at specified URL with log rotation support.

AgregateLogger forwards messages to all the loggers it is initialized with.