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

问题

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?

回答1:

Add the following to your code:

func contains(a:[(Int, Int)], v:(Int,Int)) -> Bool {
  let (c1, c2) = v
  for (v1, v2) in a { if v1 == c1 && v2 == c2 { return true } }
  return false
}

Swift is not that flexible when it comes to tuples. They do not conform to the Equatable protocol. So you must define that or use the above function.

回答2:

While tuples aren’t Equatable, you do not need to go so far as writing your own version of contains, since there is a version of contains that takes a matching predicate:

if contains(a, { $0.0 == 1 && $0.1 == 2 }) {
     // a contained (1,2)
}

While you can’t extend tuples to be equatable, you can write a version of == for tuples, which would make the above code simpler:

func ==<T: Equatable, U: Equatable>(lhs: (T,U), rhs: (T,U)) -> Bool {
    return lhs.0 == rhs.0 && lhs.1 == rhs.1
}

contains(a) { $0 == (1,2) } // returns true

It’d be nice to be able to write a version of contains for tuples, but alas, I don’t think the placeholder syntax supports it:

EDIT: as of Swift 1.2, this does now compile as you can use tuples in placeholder constraints

func contains
  <S: SequenceType, T: Equatable, U: Equatable where S.Generator.Element == (T,U)>
  (seq: S, x: (T,U)) -> Bool {
    return contains(seq) { $0.0 == x.0 && $0.1 == x.1 }
}

let a = [(1,1), (1,2)]

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

回答3:

Xcode 8.2.1 • Swift 3.0.2

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)
}

回答4:

You can't use the contains method for your problem. Also there is no embedded solution in Swift. So you need to solve that by yourself. You can create a simple function to check if a tuple in your array is the same as your tuple to check:

func checkTuple(tupleToCheck:(Int, Int), theTupleArray:[(Int, Int)]) -> Bool{
    //Iterate over your Array of tuples
    for arrayObject in theTupleArray{
        //If a tuple is the same as your tuple to check, it returns true and ends
        if arrayObject.0 == tupleToCheck.1 && arrayObject.1 == tupleToCheck.1 {
            return true
        }
    }

    //If no tuple matches, it returns false
    return false
}

回答5:

Maybe too old for this question hope someone will get help with more option.

You may use switch instead of if condition

    var somePoint = [(0, 1), (1, 0), (0, 0), (-2, 2)]
    for innerSomePoint in somePoint {
        switch innerSomePoint {
        case (0, 0):
            print("\(innerSomePoint) first and second static")
        case (_, 0):
            print("\(innerSomePoint) first dynamic second static")
        case (0, _):
            print("\(innerSomePoint) first static second dynamic")
        case (-2...2, -2...2):
            print("\(innerSomePoint) both in between values")
        default:
            print("\(innerSomePoint) Nothing found")
        }
    }

Also have some more option to do check here from apple doc

    somePoint = [(1, 1), (1, -1), (0, 0), (-2, 2)]
    for innerSomePoint in somePoint {
        switch innerSomePoint {
        case let (x, y) where x == y:
            print("(\(x), \(y)) is on the line x == y")
        case let (x, y) where x == -y:
            print("(\(x), \(y)) is on the line x == -y")
        case let (x, y):
            print("(\(x), \(y)) is just some arbitrary point")
        }
    }

来源：https://stackoverflow.com/questions/29736244/how-do-i-check-if-an-array-of-tuples-contains-a-particular-one-in-swift

标签

arrays

swift

tuples