CODEWITHSUNDEEP
swift
zaitsman
zaitsman

Reputation: 9509

Swift - collection of Optional objects .first returns double wrapped Optional

I am struggling to understand why the Array of optionals .first returns double wrapped optional in this case and how to avoid it:

class MyBanana {

}

let bananas = [MyBanana?]()
let first: MyBanana? = bananas.first

On the last line i get the following error:

Cannot convert value of type 'MyBanana??' to specified type 'MyBanana?'

Upvotes: 0

Views: 471

Answers (2)

Ortwin Gentz
Ortwin Gentz

Reputation: 54151

I solved it like this:

let first: MyBanana? = bananas.isEmpty ? nil : bananas[0]

Although, in my opinion, first should handle such a situation without complaining.

Upvotes: 1

Ken Mueller
Ken Mueller

Reputation: 4173

You have an array of Optional MyBananas, and .first gives you back the first element of the array as an optional.

Calling .first on an array is equivalent to this code snippet:

if array.count == 0 {
    return nil
} else {
    return array[0]
}

It's a safe way of getting the first element of an array.

When you call .first on an array of type Array<T>, you get back an element of type T?. bananas is of type Array<MyBanana?>. Therefore, T = MyBanana? and .first gives back an element of type T? = MyBanana??.

I would strongly recommend you do not keep an array of optional elements, since .first already gives you back an optional.

Upvotes: 2

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