Check string for nil & empty

Question

Is there a way to check strings for nil and \"\" in Swift? In Rails, I can use blank() to check.

I currently have this, but i

Answer 1

With Swift 5, you can implement an Optional extension for String type with a boolean property that returns if an optional string is empty or has no value:

extension Optional where Wrapped == String {

    var isEmptyOrNil: Bool {
        return self?.isEmpty ?? true
    }

}

However, String implements isEmpty property by conforming to protocol Collection. Therefore we can replace the previous code's generic constraint (Wrapped == String) with a broader one (Wrapped: Collection) so that Array, Dictionary and Set also benefit our new isEmptyOrNil property:

extension Optional where Wrapped: Collection {

    var isEmptyOrNil: Bool {
        return self?.isEmpty ?? true
    }

}

---

Usage with Strings:

let optionalString: String? = nil
print(optionalString.isEmptyOrNil) // prints: true

let optionalString: String? = ""
print(optionalString.isEmptyOrNil) // prints: true

let optionalString: String? = "Hello"
print(optionalString.isEmptyOrNil) // prints: false

Usage with Arrays:

let optionalArray: Array<Int>? = nil
print(optionalArray.isEmptyOrNil) // prints: true

let optionalArray: Array<Int>? = []
print(optionalArray.isEmptyOrNil) // prints: true

let optionalArray: Array<Int>? = [10, 22, 3]
print(optionalArray.isEmptyOrNil) // prints: false

---

Sources:

• swiftbysundell.com - Extending optionals in Swift
• objc.io - Swift Tip: Non-Empty Collections

Answer 2

Create a String class extension:

extension String
{   //  returns false if passed string is nil or empty
    static func isNilOrEmpty(_ string:String?) -> Bool
    {   if  string == nil                   { return true }
        return string!.isEmpty
    }
}// extension: String

Notice this will return TRUE if the string contains one or more blanks. To treat blank string as "empty", use...

return string!.trimmingCharacters(in: CharacterSet.whitespaces).isEmpty

... instead. This requires Foundation.

Use it thus...

if String.isNilOrEmpty("hello world") == true 
{   print("it's a string!")
}

Answer 3

helpful when getting value from UITextField and checking for nil & empty string

@IBOutlet weak var myTextField: UITextField!

Heres your function (when you tap on a button) that gets string from UITextField and does some other stuff

@IBAction func getStringFrom_myTextField(_ sender: Any) {

guard let string = myTextField.text, !(myTextField.text?.isEmpty)!  else { return }
    //use "string" to do your stuff.
}

This will take care of nil value as well as empty string.

It worked perfectly well for me.

Answer 4

var str: String? = nil

if str?.isEmpty ?? true {
    print("str is nil or empty")
}

str = ""

if str?.isEmpty ?? true {
    print("str is nil or empty")
}

Answer 5

If you want to access the string as a non-optional, you should use Ryan's Answer, but if you only care about the non-emptiness of the string, my preferred shorthand for this is

if stringA?.isEmpty == false {
    ...blah blah
}

Since == works fine with optional booleans, I think this leaves the code readable without obscuring the original intention.

If you want to check the opposite: if the string is nil or "", I prefer to check both cases explicitly to show the correct intention:

if stringA == nil || stringA?.isEmpty == true {
    ...blah blah
}

Answer 6

You can create your own custom function, if that is something you expect to do a lot.

func isBlank (optionalString :String?) -> Bool {
    if let string = optionalString {
        return string.isEmpty
    } else {
        return true
    }
}



var optionalString :String? = nil

if isBlank(optionalString) {
    println("here")
}
else {
    println("there")
}