Is there a Swift alternative for NSLog(@"%s", __PRETTY_FUNCTION__)

Question

In Objective C you can log the method that is being called using:

NSLog(@"%s", __PRETTY_FUNCTION__)

Usually this is used from a logging macro.

Although Swift does not support macro's (I think) I still would like to use a generic log statement that includes the name of the function that was called. Is that possible in Swift?

Update: I now use this global function for logging which can be found here: https://github.com/evermeer/Stuff#print And which you can install using:

pod 'Stuff/Print'

Here is the code:

public class Stuff {

    public enum logLevel: Int {
        case info = 1
        case debug = 2
        case warn = 3
        case error = 4
        case fatal = 5
        case none = 6

        public func description() -> String {
            switch self {
            case .info:
                return "❓"
            case .debug:
                return "✳️"
            case .warn:
                return "⚠️"
            case .error:
                return "🚫"
            case .fatal:
                return "🆘"
            case .none:
                return ""
            }
        }
    }

    public static var minimumLogLevel: logLevel = .info

    public static func print<T>(_ object: T, _ level: logLevel = .debug, filename: String = #file, line: Int = #line, funcname: String = #function) {
        if level.rawValue >= Stuff.minimumLogLevel.rawValue {
            let dateFormatter = DateFormatter()
            dateFormatter.dateFormat = "MM/dd/yyyy HH:mm:ss:SSS"
            let process = ProcessInfo.processInfo
            let threadId = "?"
            let file = URL(string: filename)?.lastPathComponent ?? ""
            Swift.print("\n\(level.description()) .\(level) ⏱ \(dateFormatter.string(from: Foundation.Date())) 📱 \(process.processName) [\(process.processIdentifier):\(threadId)] 📂 \(file)(\(line)) ⚙️ \(funcname) ➡️\r\t\(object)")
        }
    }
}

Which you can use like this:

Stuff.print("Just as the standard print but now with detailed information")
Stuff.print("Now it's a warning", .warn)
Stuff.print("Or even an error", .error)

Stuff.minimumLogLevel = .error
Stuff.print("Now you won't see normal log output")
Stuff.print("Only errors are shown", .error)

Stuff.minimumLogLevel = .none
Stuff.print("Or if it's disabled you won't see any log", .error)    

Which will result in:

✳️ .debug ⏱ 02/13/2017 09:52:51:852 📱 xctest [18960:?] 📂 PrintStuffTests.swift(15) ⚙️ testExample() ➡️
    Just as the standard print but now with detailed information

⚠️ .warn ⏱ 02/13/2017 09:52:51:855 📱 xctest [18960:?] 📂 PrintStuffTests.swift(16) ⚙️ testExample() ➡️
    Now it's a warning

🚫 .error ⏱ 02/13/2017 09:52:51:855 📱 xctest [18960:?] 📂 PrintStuffTests.swift(17) ⚙️ testExample() ➡️
    Or even an error

🚫 .error ⏱ 02/13/2017 09:52:51:855 📱 xctest [18960:?] 📂 PrintStuffTests.swift(21) ⚙️ testExample() ➡️
    Only errors are shown

Answer 1

Swift has #file, #function, #line and #column. From Swift Programming Language:

#file - String - The name of the file in which it appears.

#line - Int - The line number on which it appears.

#column - Int - The column number in which it begins.

#function - String - The name of the declaration in which it appears.

Answer 2

Starting from Swift 2.2 we should use:

• #file (String) The name of the file in which it appears.
• #line (Int) The line number on which it appears.
• #column (Int) The column number in which it begins.
• #function (String) The name of the declaration in which it appears.

From The Swift Programming Language (Swift 3.1) at page 894.

func specialLiterals() {
    print("#file literal from file: \(#file)")
    print("#function literal from function: \(#function)")
    print("#line: \(#line) -> #column: \(#column)")
}
// Output:
// #file literal from file: My.playground
// #function literal from function: specialLiterals()
// #line: 10 -> #column: 42

Answer 3

Swift 4
Here's my approach:

func pretty_function(_ file: String = #file, function: String = #function, line: Int = #line) {

    let fileString: NSString = NSString(string: file)

    if Thread.isMainThread {
        print("file:\(fileString.lastPathComponent) function:\(function) line:\(line) [M]")
    } else {
        print("file:\(fileString.lastPathComponent) function:\(function) line:\(line) [T]")
    }
}

Make this a global function and just call

pretty_function()

Bonus: You will see the thread is executed on, [T] for a background thread and [M] for the Main thread.

Answer 4

As of XCode beta 6, you can use reflect(self).summary to get the class name and __FUNCTION__ to get the function name, but things are a bit mangled, right now. Hopefully, they'll come up with a better solution. It might be worthwhile to use a #define until we're out of beta.

This code:

NSLog("[%@ %@]", reflect(self).summary, __FUNCTION__)

gives results like this:

2014-08-24 08:46:26.606 SwiftLessons[427:16981938] [C12SwiftLessons24HelloWorldViewController (has 2 children) goodbyeActiongoodbyeAction]

EDIT: This is more code, but got me closer to what I needed, which I think is what you wanted.

func intFromString(str: String) -> Int
{
    var result = 0;
    for chr in str.unicodeScalars
    {
        if (chr.isDigit())
        {
            let value = chr - "0";
            result *= 10;
            result += value;
        }
        else
        {
            break;
        }
    }

    return result;
}


@IBAction func flowAction(AnyObject)
{
    let cname = _stdlib_getTypeName(self)
    var parse = cname.substringFromIndex(1)                                 // strip off the "C"
    var count = self.intFromString(parse)
    var countStr = String(format: "%d", count)                              // get the number at the beginning
    parse = parse.substringFromIndex(countStr.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))
    let appName = parse.substringToIndex(count)                             // pull the app name

    parse = parse.substringFromIndex(count);                                // now get the class name
    count = self.intFromString(parse)
    countStr = String(format: "%d", count)
    parse = parse.substringFromIndex(countStr.lengthOfBytesUsingEncoding(NSUTF8StringEncoding))
    let className = parse.substringToIndex(count)
    NSLog("app: %@ class: %@ func: %@", appName, className, __FUNCTION__)
}

It gives output like this:

2014-08-24 09:52:12.159 SwiftLessons[1397:17145716] app: SwiftLessons class: ViewController func: flowAction