Swift: Nil is incompatible with return type String

≯℡__Kan透↙ 提交于 2019-11-30 21:56:49

you have to tell the compiler that you want to return nil. How do you that? by assigning '?' after your object. For instance take a look at this code:

func newFriend(friendDictionary: [String : String]) -> Friend? {
    guard let name = friendDictionary["name"], let age = friendDictionary["age"] else {
        return nil
    }
    let address = friendDictionary["address"]
    return Friend(name: name, age: age, address: address)
}

Notice that i had to tell the compiler that my Object Friend that i'm returning is an optional 'Friend?' other wise it spill an error on me

Does your function declare an optional return type?

func foo() -> String? { ...

See more on: https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/Swift_Programming_Language/TheBasics.html

NOTE

The concept of optionals doesn’t exist in C or Objective-C. The nearest thing in Objective-C is the ability to return nil from a method that would otherwise return an object, with nil meaning “the absence of a valid object.”

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