Is there a short hand way to loop through an array and add values to another array?

Question

Is there a short hand way of doing something like this in Swift?

var serviceTypes = [String]()
for menu in menus {
    if let serviceType = menu.serviceType {
        serviceTypes += [serviceType]
    }
}

TylerP · Accepted Answer · 2020-05-20T02:17:55.423

1

In your case, since you're only adding to the other array if the serviceType is non-nil, use compactMap(_:).

If you're using Swift 5.2 or later, you can do this with KeyPaths:

let serviceTypes = menus.compactMap(\.serviceType)

If you're using a version of Swift prior to 5.2, you can use a closure:

let serviceTypes = menus.compactMap { $0.serviceType }

edited May 20 '20 at 02:17

answered May 20 '20 at 00:22

TylerP

1

There is no need to use a closure `compactMap(\.serviceType)` you can use the KeyPath – Leo Dabus May 20 '20 at 02:07
1

Thanks @LeoDabus, I had no idea you could use keypaths like that as of Swift 5.2. I'll update my answer to include that! – TylerP May 20 '20 at 02:13
You are welcome KeyPaths where introduced in Swift 4 – Leo Dabus May 20 '20 at 02:14
Yes but this functionality was not introduced until [Swift 5.2](https://github.com/apple/swift-evolution/blob/master/proposals/0249-key-path-literal-function-expressions.md). – TylerP May 20 '20 at 02:14
Yes the use with compactMap was added later – Leo Dabus May 20 '20 at 02:16
1

https://stackoverflow.com/a/32021850/2303865 you can use it with split method as well but you need to disambiguate including the parameter name – Leo Dabus May 20 '20 at 02:24

score 1 · Answer 2 · answered May 20 '20 at 00:28

1

map() is your friend! (And it has friends, flatMap() and compactMap().)

var serviceTypes = menus.compactMap {$0.serviceType}

answered May 20 '20 at 00:28

Craig Temple

2 Answers2