CODEWITHSUNDEEP
iosswift
Morgan Wilde
Morgan Wilde

Reputation: 17303

Initialising an array of two tuples fails

I have a simple function that returns an array of tuples

func findNodeNeighbors(node: Node) -> [(node: Node, distance: Double)] {
    var neighbors = [(node: Node, distance: Double)]()
    var nodeLinks = linksWith(node)
    for link in nodeLinks {
        neighbors.append((node: link.otherNodeLinkedWith(node), distance: link.length))
    }
    return neighbors
}

But this turns out is an error Invalid use of () to call a clue of non-function type on the first line of the function body.

If instead I declare the type for neighbors explicitly, everything is fine.

var neighbors: [(node: Node, distance: Double)] = []

How come?

I've read that it is preferred to declare arrays by initialising them and allowing for implicit type inference.

Upvotes: 3

Views: 76

Answers (3)

simons
simons

Reputation: 2400

what if I want an empty array as the initial value?

I am not 100% certain - but I think that another way you can quickly get around this issue currently is by declaring the tuple using a typealias.

Eg:

typealias Test = (Node, Double)

func findNodeNeighbors(node: Node) -> [Test] {
    var neighbors = [Test]()
    //etc
}

Upvotes: 2

Airspeed Velocity
Airspeed Velocity

Reputation: 40965

Pretty certain this is a bug in Swift's parser, specifically to do with the [Type] sugar in combination with named tuples.

var neighbors = Array<(node: Node, distance: Double)>() (which should be identical to [(node: Node, distance: Double)]()) works fine.

edit: looks like the dictionary equivalent has the same problem

Works fine:

var d = Dictionary<Int,(x: Int, y: Int)>()

Busted:

var d = [Int:(x: Int, y: Int)]()

Upvotes: 4

Farlei Heinen
Farlei Heinen

Reputation: 5899

You should initialise the array using default values:

var neighbors = [(node: node, distance: 0.0)]

Upvotes: 0

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