Optional in Swift

Question

I have some code in Swift on repl.it

let name = readLine()
print("Hello, \(name)!")

When I run it, I type in my name, and then it says "Hello, Optional("Andrew")!". I tried making the variable an optional string, like so:

let name: String? = readLine()
print("Hello, \(name)!")

Same result. What is wrong, and how do I avoid these errors?

Please read [Optionals](https://docs.swift.org/swift-book/LanguageGuide/TheBasics.html#ID330) in the Swift Language Guide. And as you are a beginner you are encouraged to read the entire Guide — vadian, Dec 18 '19 at 19:48
Note the print output `Optional("Andrew")!` does not mean the string is equal to that; what you're seeing there is the output of the `debugDescription` for that value. — shim, Dec 18 '19 at 19:53
Does this answer your question? [What is an optional value in Swift?](https://stackoverflow.com/questions/24003642/what-is-an-optional-value-in-swift) — fhe, Dec 18 '19 at 20:13

score 2 · Accepted Answer · edited Dec 18 '19 at 19:54

That's not an error, that's how optionals work!

Clearly the readline() function returns an optional string, which is why you have the issue in the first call.

readline()'s method signature is:

func readLine(strippingNewline: Bool = true) -> String?

So it will always return an optional string.

So if you wish to print without optionals just do:

print("Hello, \(name!)!")

You could also follow best practice and safely 'unwrap':

if let name = readLine() {
  print(name)
}

score 0 · Answer 2 · edited Dec 18 '19 at 19:56

0

You should safely unwrap optionals:

if let name = readLine() {
  print(name)
}

or

guard let name = readLine() else { return }
print(name)

edited Dec 18 '19 at 19:56

shim

answered Dec 18 '19 at 19:47

Sh_Khan

score 0 · Answer 3 · answered Dec 18 '19 at 19:50

0

readLine() can most likely also return nil — that's why an optional String is returned.

Use optional binding so that you only use the name if it actually contains a value.

if let name = readLine() {
    print("Hello, \(name)!")
}

answered Dec 18 '19 at 19:50

fhe

3 Answers3