Simple Swift logging functions

log.swift

import Foundation

extension String {    
    /// Return last path component.
    public var lastPathComponent: String {
        return (self as NSString).lastPathComponent
    }
}

/// Write a message to the system log.
///
/// The message will be prepended with function/file/line information.
func log(_ message: String,
         _ function: String = #function,
         _ file: String = #file,
         _ line: Int = #line) {
    NSLog("\(function) (\(file.lastPathComponent):\(line)): \(message)")
}

/// Write an error message to the system log.
///
/// The message will be prepended with function/file/line information.
func log_error(_ message: String,
               _ function: String = #function,
               _ file: String = #file,
               _ line: Int = #line) {
    NSLog("ERROR: \(function) (\(file.lastPathComponent):\(line)): \(message)")
}

/// Write a warning message to the system log.
///
/// The message will be prepended with function/file/line information.
func log_warning(_ message: String,
                 _ function: String = #function,
                 _ file: String = #file,
                 _ line: Int = #line) {
    NSLog("WARNING: \(function) (\(file.lastPathComponent):\(line)): \(message)")
}

Example use:

log("Hello, world!")

Log output:

2018-09-03 15:13:28.992075-0400 Hello[93427:6074998] main(args:) (Hello.swift:10) Hello, world!