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

Using the guard statement

I was using Swift for a while before I learned about the guard statement. Now I am a big fan. It is used similarly to the if statement, but it allows for early return and just makes for much cleaner code in general.

To use guard when checking to make sure that a string is neither nil nor empty, you can do the following:

let myOptionalString: String? = nil

guard let myString = myOptionalString, !myString.isEmpty else {
    print("String is nil or empty.")
    return // or break, continue, throw
}

/// myString is neither nil nor empty (if this point is reached)
print(myString)

This unwraps the optional string and checks that it isn't empty all at once. If it is nil (or empty), then you return from your function (or loop) immediately and everything after it is ignored. But if the guard statement passes, then you can safely use your unwrapped string.

See Also

• Statements documentation
• The Guard Statement in Swift 2

Answer 2

you can use this func

 class func stringIsNilOrEmpty(aString: String) -> Bool { return (aString).isEmpty }

Answer 3

Using isEmpty

"Hello".isEmpty  // false
"".isEmpty       // true

Using allSatisfy

extension String {
  var isBlank: Bool {
    return allSatisfy({ $0.isWhitespace })
  }
}

"Hello".isBlank        // false
"".isBlank             // true

Using optional String

extension Optional where Wrapped == String {
  var isBlank: Bool {
    return self?.isBlank ?? true
  }
}

var title: String? = nil
title.isBlank            // true
title = ""               
title.isBlank            // true

Reference : https://useyourloaf.com/blog/empty-strings-in-swift/

Answer 4

Swift 3 solution Use the optional unwrapped value and check against the boolean.

if (string?.isempty == true) {
    // Perform action
}

Answer 5

If you are using Swift 2, here is an example my colleague came up with, which adds isNilOrEmpty property on optional Strings:

protocol OptionalString {}
extension String: OptionalString {}

extension Optional where Wrapped: OptionalString {
    var isNilOrEmpty: Bool {
        return ((self as? String) ?? "").isEmpty
    }
}

You can then use isNilOrEmpty on the optional string itself

func testNilOrEmpty() {
    let nilString:String? = nil
    XCTAssertTrue(nilString.isNilOrEmpty)

    let emptyString:String? = ""
    XCTAssertTrue(emptyString.isNilOrEmpty)

    let someText:String? = "lorem"
    XCTAssertFalse(someText.isNilOrEmpty)
}

Answer 6

In my opinion, the best way to check the nil and empty string is to take the string count.

var nilString : String?
print(nilString.count) // count is nil

var emptyString = ""
print(emptyString.count) // count is 0

// combine both conditions for optional string variable
if string?.count == nil || string?.count == 0 {
   print("Your string is either empty or nil")
}