Swift LogUtils - allows to redirect log entries to /Library/Logs/<AppName>.log

AppDelegate.swift

//
//  AppDelegate.swift
//  SwiftApp
//
//  Created by Vito Tardia on 02/04/15.
//  Copyright (c) 2014 Vito Tardia. All rights reserved.
//

import Cocoa
import Foundation

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

    @IBOutlet weak var window: NSWindow!
    
    var appInfo: Dictionary<NSObject,AnyObject>
    var appName: String!
    
    override init() {
        
        // Init local parameters
        self.appInfo = CFBundleGetInfoDictionary(CFBundleGetMainBundle()) as Dictionary
        self.appName = appInfo["CFBundleName"] as! String
        
        // Init parent
        super.init()
        
        // Other init below...

        SetCustomLogFilename(self.appName)
        
    }
    
    func applicationDidFinishLaunching(aNotification: NSNotification) {

        // Insert code here to initialize your application
        InfoLog(String(format:"Application %@ starting", self.appName))
        DebugLog(String(format:"A debug message: %@", "BBB"))
        
        var test = TestObj()
    }

    func applicationWillTerminate(aNotification: NSNotification) {
        
        // Insert code here to tear down your application
        InfoLog(String(format:"Application %@ will terminate", self.appName))
    }


}

LogUtils.swift

//
//  LogUtils.swift
//  SwiftApp
//
//  Created by Vito Tardia on 02/04/15.
//  Copyright (c) 2014 Vito Tardia. All rights reserved.
//

import Foundation

var logFileHandle: NSFileHandle?
var original_stderr: Int32?;

#if DEBUG
    func DebugLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
        return { NSLog("<Debug>: " + message + " [" + file + ":%i]", line) }()
    }

    func InfoLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
        return { NSLog("<Info>: " + message + " [" + file + ":%i]", line) }()
    }

    func WarningLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
        return { NSLog("<Warning>: " + message + " [" + file + ":%i]", line) }()
    }

    func ErrorLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
        return { NSLog("<Error>: " + message + " [" + file + ":%i]", line) }()
    }
#else
    func DebugLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
    }

    func InfoLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
        return { NSLog("<Info>: " + message) }()
    }
    
    func WarningLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
        return { NSLog("<Warning>: " + message) }()
    }
    
    func ErrorLog(message: String, file: String = __FILE__, line: Int = __LINE__) {
        return { NSLog("<Error>: " + message) }()
    }
#endif


// Redirect log to /Library/Logs/<AppName>.log
func SetCustomLogFilename(name: String) {

    // Search log directory path
    if let logDirectory: NSURL = NSFileManager.defaultManager().URLForDirectory(NSSearchPathDirectory.LibraryDirectory, inDomain: NSSearchPathDomainMask.UserDomainMask, appropriateForURL: nil, create: true, error: nil)?.URLByAppendingPathComponent("Logs/") {
        
        // Calculate full log file path
        if let logFilePath = logDirectory.URLByAppendingPathComponent(String(format:"%@.log", name)) as NSURL! {
            
            // Save STDERR
            var stderr = NSFileHandle.fileHandleWithStandardError()
            original_stderr = dup(stderr.fileDescriptor)
            
            // Create an empty log file at path, NSFileHandle doesn't do it!
            if !NSFileManager.defaultManager().isWritableFileAtPath(logFilePath.path!) {
                "".writeToFile(logFilePath.path!, atomically: true, encoding: NSUTF8StringEncoding, error: nil)
            }
            
            
            if let logFileHandle = NSFileHandle(forWritingAtPath: logFilePath.path!) {
                
                // (Try to) Redirect STDERR to log file
                var err:Int32? = dup2(logFileHandle.fileDescriptor, stderr.fileDescriptor)
                
                // Something went wrong
                if (err == -1) {
                    ErrorLog(String(format:"Could not redirect stderr, error %d", errno))
                }
            }
        }
    }
}

TestObj.swift

//
//  TestObj.swift
//  SwiftApp
//
//  Created by Vito Tardia on 02/04/15.
//  Copyright (c) 2014 Vito Tardia. All rights reserved.
//

import Foundation


class TestObj {
    
    var name: String
    
    init() {
        self.name = "Foo"
        InfoLog(String(format:"Loading: %@", self.name))
    }
}