Logging Method signature using swift

Question

I am trying to rewrite my logging class and I would like to know how to substitute PRETTY_FUNCTION or NSStringFromSelector(_cmd) in a swift file in order to track the method calls?

Answer 1

Special literals in swift are as follows (from [the swift guide]

#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.

---

Prior to Swift 2.2b4, these were

(https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Expressions.html)):

__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.

You can use these in logging statements like so:

println("error occurred on line \(__LINE__) in function \(__FUNCTION__)")

Answer 2

Check out a new library I've just published: https://github.com/DaveWoodCom/XCGLogger

It's a debug logging library for Swift.

The key to being able to use the #function macros, is to set them as default values to your logging function. The compiler will then fill them in using the expected values.

func log(logMessage: String, functionName: String = #function) {
    print("\(functionName): \(logMessage)")
}

Then just call:

log("my message")

And it works as expected giving you something like:

whateverFunction(): my message

More info on how this works: https://www.cerebralgardens.com/blog/entry/2014/06/09/the-first-essential-swift-3rd-party-library-to-include-in-your-project

Answer 3

I'd use something like this:

func Log(message: String = "", _ path: String = __FILE__, _ function: String = __FUNCTION__) {
    let file = path.componentsSeparatedByString("/").last!.componentsSeparatedByString(".").first! // Sorry
    NSLog("\(file).\(function): \(message)")
}

Improvements compared to previous answers:

• Uses NSLog, not print/println
• Does not use lastPathComponent which is not available on Strings anymore
• The log message is optional