Swift equivalent to `[NSDictionary initWithObjects: forKeys:]`

Question

Is there an equivalent for Swift's native Dictionary to [NSDictionary initWithObjects: forKeys:]?

Say I have two arrays with keys and values and want to put them in a dictionary. In Objective-C I'd do it like this:

NSArray *keys = @[@"one", @"two", @"three"];
NSArray *values = @[@1, @2, @3];
NSDictionary *dict = [[NSDictionary alloc] initWithObjects: values forKeys: keys];

Of course I can iterate with a counter through both arrays, use a var dict: [String:Int] and add stuff step by step. But that doesn't seem to be a good solution. Using zip and enumerate are probably better ways of iterating over both at the same time. However this approach means having a mutable dictionary, not an immutable one.

let keys = ["one", "two", "three"]
let values = [1, 2, 3]
// ???
let dict: [String:Int] = ["one":1, "two":2, "three":3] // expected result

Answer 1

As of Swift 4 you can create a dictionary directly from a sequence of key/value pairs:

let keys = ["one", "two", "three"]
let values = [1, 2, 3]

let dict = Dictionary(uniqueKeysWithValues: zip(keys, values))

print(dict) // ["one": 1, "three": 3, "two": 2]

This assumes that all keys are different, otherwise it will abort with a runtime exception.

If the keys are not guaranteed to be distinct then you can do

let keys = ["one", "two", "one"]
let values = [1, 2, 3]

let dict = Dictionary(zip(keys, values), uniquingKeysWith: { $1 })

print(dict) // ["one": 3, "two": 2]

The second argument is a closure which determines which value "wins" in the case of duplicate keys.

Answer 2

You can simply use the Swift equivalent of initWithObjects:forKeys:

let keys = ["one", "two", "three"]
let values = [1, 2, 3]
var dict = NSDictionary.init(objects: values, forKeys: keys)

Answer 3

Working pure Swift solution with structs. Use zip to iterate through your two arrays as a tuple, and then create a dictionary for each key, value in the tuple.

struct SomeStruct {
    var someVal: Int?
}

var keys = [String]()
var values = [SomeStruct]()

for index in 0...5 {
    keys.append(String(index))
    values.append(SomeStruct(someVal: index))
}

var dict = [String : Any]()

for (key, value) in zip(keys, values) {
    dict[key] = value
}

print(dict) // "["4": SomeStruct(someVal: Optional(4)), "2": SomeStruct(someVal: Optional(2)), "1": SomeStruct(someVal: Optional(1)), "5": SomeStruct(someVal: Optional(5)), "0": SomeStruct(someVal: Optional(0)), "3": SomeStruct(someVal: Optional(3))]"

You could also use forEach on zip:

var dict = [String : Any]()
zip(keys, values).forEach { dict[$0.0] = $0.1 }
print(dict) // "["4": SomeStruct(someVal: Optional(4)), "2": SomeStruct(someVal: Optional(2)), "1": SomeStruct(someVal: Optional(1)), "5": SomeStruct(someVal: Optional(5)), "0": SomeStruct(someVal: Optional(0)), "3": SomeStruct(someVal: Optional(3))]\n"