How do I check if an array of tuples contains a particular one in Swift?

Question

Consider the following Swift code.

var a = [(1, 1)]

if contains(a, (1, 2)) {
    println("Yes")
}

All I need is to check if a contains the tuple but the code leads to error.

Cannot find an overload for 'contains' that accepts an argument list of type '([(Int, Int)], (Int, Int))'

Why so and how to use contains properly?

Answer 1

You can use a predicate and check for equality:

let tuples = [(1, 1), (0, 1)]

let tuple1 = (1, 2)
let tuple2 = (0, 1)

if tuples.contains(where: {$0 == tuple1}) {
    print(true)
} else {
    print(false)    // false
}

if tuples.contains(where: {$0 == tuple2}) {
    print(true)    // true
} else {
    print(false)
}

You can also create your own contains methods that takes generic tuples:

extension Sequence  {
    func contains<T, U>(_ tuple: (T, U)) -> Bool where T: Equatable, U: Equatable, Element == (T,U) {
        contains { $0 == tuple }
    }
    func contains<T, U, V>(_ tuple: (T, U, V)) -> Bool where T: Equatable, U: Equatable, V: Equatable, Element == (T,U,V) {
        contains { $0 == tuple }
    }
    func contains<T, U, V, W>(_ tuple: (T, U, V, W)) -> Bool where T: Equatable, U: Equatable, V: Equatable, W: Equatable,Element == (T, U, V, W) {
        contains { $0 == tuple }
    }
    func contains<T, U, V, W, X>(_ tuple: (T, U, V, W, X)) -> Bool where T: Equatable, U: Equatable, V: Equatable, W: Equatable, X: Equatable, Element == (T, U, V, W, X) {
        contains { $0 == tuple }
    }
    func contains<T, U, V, W, X, Y>(_ tuple: (T, U, V, W, X, Y)) -> Bool where T: Equatable, U: Equatable, V: Equatable, W: Equatable, X: Equatable, Y: Equatable, Element == (T, U, V, W, X, Y) {
        contains { $0 == tuple }
    }
}

---

if tuples.contains(tuple1) {
    print(true)
} else {
    print(false)    // false
}

if tuples.contains(tuple2) {
    print(true)    // true
} else {
    print(false)
}