'NSLog' is unavailable: Variadic function is unavailable in swift

I'm new to swift. when I'm learning just basics I got this error at `NSLog`

**Here is my code :**

import UIKit

class ViewController: UIViewController {

var myString: NSString?

override func viewDidLoad() {
super.viewDidLoad()
myString = "himanth"
print(myString)
NSLog("%@" , myString)
// Do any additional setup after loading the view, typically from a nib.
}

override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}


}

If I am declaring `myString` like this

var myString: NSString!

It's fine to use `NSLog` and I can able to see console as well.

But declaring string like this causing problem

var myString: NSString?

It reflects at `NSLog` and showing error.

What is the problem with that?

`NSLog` does not support any types except `String`. You cannot pass, i.e. your custom struct / enum instance as NSLog variadic argument.

Instead use `description` variable to show up necessary details about your instance. Your class / struct / enum could conform `CustomStringConvertible` to unify the way to access `description` variable as well.

If you declare `var myString: NSString?` as an optional then you need to make sure it has a value before you pass it to the `NSLog`.

So you could do it like this then `NSLog("%@" , myString!)`. If `myString` is nil and you put `!` the program will crash and you will get

fatal error: unexpectedly found nil while unwrapping an Optional value.

But if it has a value the program will continue as normal and print out

2016-10-03 10:26:25.077 Swift3.0[65214:1579363] Test

I wrote `myString = "Test"`.

Another example as [@Grimxn][1] mentioned is the coalescing operator.

NSLog("%@", myString ?? "<nil>")


[1]:

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Have the same problem, accepted answer doesn't help.

func handleSomeResp(_ response: DataResponse<Any>) {
NSLog("handle error: %@", response)
}

as you see, there is nothing about optionals.
I guess it because of `<Any>`, and any type, unclear for NSLog, watch similar problem [here][1]: .
Edit this answer if you have a solution to parse generics for NSLog.


[1]:

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`NSLog()` cannot print Swift Optionals.


let optional: String?
NSLog("%@", optional) // 'NSLog' is unavailable: Variadic function is unavailable

let nonOptional: String
NSLog("%@", nonOptional) // Ok!

NSLog("%@", optional ?? "value-if-nil") // Ok!

Fix by passing a non-optional value to `NSLog()` instead.

NOTE:

`print()` ***can*** print Swift Optionals.