Swift: format console-log - swift

Question

is there any possibility to create a custom log function?
This is how the default println("hello world") looks like:
2015-03-04 18:33:55.788 MyApp[12345:671253923] Hello World
I would like to output something like:
18:33 MyClass > myFunc [line 1] Hello World

Answer 1

First, for the time, you can get the current hour and minute as String:
func printTime()->String{
let date = NSDate()
let calendar = NSCalendar.currentCalendar()
let components = calendar.components(.CalendarUnitHour | .CalendarUnitMinute, fromDate: date)
let hour = components.hour
let minutes = components.minute
return "\(hour):\(minutes)"
}
And for the function etc. you can use the Swift Literal Expressions __FILE__, __FUNCTION__ and __LINE__.
But you don't want to set it each time you want to log. So you could do something like that:
func prettyPrint(print: String, file:String = __FILE__, functionName: String = __FUNCTION__, line:Int = __LINE__) {
println("\(printTime()) \(file) > \(functionName) [line \(line)] \(print)")
}
You call prettyPrint like that:
prettyPrint("hey")
And you will get the following output:
/Path/To/Your/File/MyClass.swift > hello [line 81] hey
But as you only want the name of your class, you can remove the path with the following function:
func getFile(path:String = __FILE__)->String{
var parts = path.componentsSeparatedByString("/")
return parts[parts.count-1]
}
Or, as ChikabuZ mentioned in his answer you can directly check the class:
let className = NSStringFromClass(self.classForCoder).pathExtension
Final Function
And here the final function(s):
func getFile(path:String = __FILE__)->String{
var parts = path.componentsSeparatedByString("/")
return parts[parts.count-1]
}
func prettyPrint(print: String, functionName: String = __FUNCTION__, line:Int = __LINE__) {
println("\(printTime()) \(getFile()) > \(functionName) [line \(line)] \(print)")
}
func printTime()->String{
let date = NSDate()
let calendar = NSCalendar.currentCalendar()
let components = calendar.components(.CalendarUnitHour | .CalendarUnitMinute, fromDate: date)
let hour = components.hour
let minutes = components.minute
return "\(hour):\(minutes)"
}
And the result will be:
MyClass.swift > hello [line 81] hey
You should also note #emaloney's answer to this question. Specifically that
println()-based solutions result in output being captured by the Apple System Log (ASL).
Ideally switch to NSLog or a full blown logging system

Answer 2

You should make an extension to NSObject, something like this:
class MyClass: NSObject
{
func myFunc()
{
myPrint("Hello World")
}
}
extension NSObject
{
func myPrint(text: String)
{
let timeFormatter = NSDateFormatter()
timeFormatter.dateStyle = NSDateFormatterStyle.NoStyle
timeFormatter.timeStyle = NSDateFormatterStyle.ShortStyle
let time = timeFormatter.stringFromDate(NSDate())
let className = NSStringFromClass(self.classForCoder).pathExtension
let function = __FUNCTION__
let line = "\(__LINE__)"
let result = time + " " + className + " > " + function + " " + line + " " + text
println(result)
}
}
let myClass = MyClass()
myClass.myFunc()

Answer 3

Unfortunately, none of the println()-based solutions result in output being captured by the Apple System Log (ASL).
The ASL is the logging facility provided by the Mac OS and iOS that is used by NSLog() (and on a Mac is visible through the Console application). Because NSLog() uses ASL, log entries recorded by NSLog() will be visible through the device console. Messages logged through println() will not be captured in ASL, and as a result, provide no opportunity to go back to the console for diagnostic purposes after something has happened.
There are two big downsides to NSLog(), however: (1) you can't customize the output format, and (2) it does a lot of work on the calling thread and can therefore negatively impact performance.
CleanroomLogger is a new Swift-based open-source API for logging. If you're familiar with log4j or CocoaLumberjack, then you'll understand CleanroomLogger.
You can customize your own output format by providing your own LogFormatter implementation to ensure that your log messages are formatted exactly as you want.
For more information on CleanroomLogger, visit the GitHub project page.