Remove println() for release version iOS Swift

Question

I would like to globally ignore all println() calls in my Swift code if I am not in a Debug build. I can\'t find any robust step by step instructions for this a

Answer 1

I ended up using this:

#if DEBUG
func dLog(_ item: @autoclosure () -> Any, _ file: String = #file, _ function: String = #function, _ line: Int = #line) {
    print("\(Date()) [\((file as NSString).lastPathComponent):\(line) \(function)] \(item())")
}
#else
func dLog(_ item: @autoclosure () -> Any) {}
#endif

It is quite compact, prints some useful informations (timestamp, swift file name, code line, function name) and at least in my tests I could not find any logged strings in the application binary file when opened in hex editior.

Answer 2

Here is a function that I use, which works perfectly in Swift 3:

func gLog<T>( _ object: @autoclosure() -> T, _ file: String = #file, _ function: String = #function, _ line: Int = #line)
    {
    #if DEBUG
        let value = object()
        let stringRepresentation: String

        if let value = value as? CustomDebugStringConvertible
            {
            stringRepresentation = value.debugDescription
            }
        else if let value = value as? CustomStringConvertible
            {
            stringRepresentation = value.description
            }
        else
            {
            fatalError("gLog only works for values that conform to CustomDebugStringConvertible or CustomStringConvertible")
            }

        let fileURL = NSURL(string: file)?.lastPathComponent ?? "Unknown file"
        let queue = Thread.isMainThread ? "UI" : "BG"
    let gFormatter = DateFormatter()
    gFormatter.dateFormat = "HH:mm:ss:SSS"
        let timestamp = gFormatter.string(from: Date())

        print("✅ \(timestamp) {\(queue)} \(fileURL) > \(function)[\(line)]: " + stringRepresentation + "\n")
    #endif
    }

Here is an example of the output it generates:

Explanation:

• the green checkmark is used to enable you to quickly see your print (gLog) messages in the console, where they can sometimes get lost in a sea of other messages

• the time/date stamp

• the thread it is being run on -- in my case it is either the MainThread (which I call UI), or not the MainThread (which I call BG, for background thread)

• the name of the file that the gLog message resides in

• the function within the file that the gLog message resides in

• the line number of the gLog message

• the actual gLog message you would like to print out

Hope this is useful to someone else!

Answer 3

You could define debug_println whose contents would be roughly:

#if DEBUG
  println()
#endif

Answer 4

XCode 8 introduced a few new build settings.
In particular one referred to Active Compilation Conditions does in a similar way what Other Flags settings did.

"Active Compilation Conditions" is a new build setting for passing conditional compilation flags to the Swift compiler.

As per XCode 8 (tested in 8.3.2) you will get this by default:

So without any config you can write the following:

#if DEBUG
    print("⚠️ Something weird happened")
#endif

I strongly recommend you that if you use this approach extensively create a class/struct/function that wraps this logging logic. You may want to extend this further down the road.

Answer 5

My Project was developed in Objective C, but from the past year I have started merging new code in Swift, So In Swift below solution worked for me, I have added that code in My Swift constant file :

func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {
    #if DEBUG
    items.forEach {
        Swift.print($0, separator: separator, terminator: terminator)
    }
    #endif
}

Answer 6

My Solution is use this code in AppDelegate before class

// Disable console log in live app
#if !arch(x86_64) && !arch(i386)
    public func debugPrint(items: Any..., separator: String = " ", terminator: String = "\n") {

    }
    public func print(_ items: Any..., separator: String = " ", terminator: String = "\n") {

    }
#endif

class AppDelegate: UIResponder, UIApplicationDelegate {
// App Delegate Code 

}