CODEWITHSUNDEEP
swift
user4387360
user4387360

Reputation:

Cannot invoke 'append' with an argument list of type'(String)'

What is wrong here and how to solve this problem?

struct Venue {
    let building: String
    var rooms: [String]?
}

func addRoom(building: String, room: String) {
    if let venueIndex = find(venues.map {$0.building}, building) {
        venues[venueIndex].rooms.append(room) //Cannot invoke 'append' with an argument list of type'(String)'
    }
}

var venues: [Venue] = [...]

Upvotes: 3

Views: 4175

Answers (1)

Airspeed Velocity
Airspeed Velocity

Reputation: 40965

The problem is that venues[venueIndex].rooms is not a [String] but a [String]?. Optionals don’t have an append method – the value wrapped inside them might, but they don’t.

You could use optional chaining to do the append in the case where it isn’t nil:

venues[venueIndex].rooms?.append(room)

But you may instead want to initialize rooms to an empty index instead when it is nil, in which case you need to do a slightly messier assignment rather than an append:

venues[venueIndex].rooms = (venues[venueIndex].rooms ?? []) + [room]

However, it is worth asking yourself, does rooms really need to be optional? Or could it just be a non-optional array with a starting value of empty? If so, this will likely simplify much of your code.

Upvotes: 5

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