Is there a built in stack implementation in Swift? - swift

Question

I want to use Stack in my swift code. I couldn't find any inbuilt stack implementation in Swift like java.util.Stack in Java.
I could implement my own Stack in swift but I would prefer a built-in one.

Answer 1

No, but you could implement your own pretty easily
struct Stack {
private var array: [Any] = []
mutating func push(_ element: Any) {
array.append(element)
}
mutating func pop() -> Any? {
return array.popLast()
}
func peek() -> Any? {
guard let top = array.last else { return nil }
return top
}
}

Answer 2

There is an implementation in the documentation at:
https://docs.swift.org/swift-book/LanguageGuide/Generics.html
that is also type agnostic.
struct Stack<Element> {
var items = [Element]()
mutating func push(_ item: Element) {
items.append(item)
}
mutating func pop() -> Element {
return items.removeLast()
}
}

Answer 3

Finally, Apple has released Swift Swift Collections. The Collections package has an implementation of Deque. I can use this as a Stack.

Answer 4

Learned GenericStack with Swift 5.7.1 with Xcode 14:
1. First make a Protocol Stackable :
protocol Stackable {
associatedtype ObjectType
func push(value:ObjectType)
func pop()
func peek()->ObjectType?
}
2. Make a GenericStack class using Stackable :
class GenericStack<T>:Stackable {
private var list:[T] = [T]()
public var elements:[T]{
return list
}
func push(value: T) {
list.append(value)
}
func pop() {
if !list.isEmpty {
list.removeLast()
}
}
func peek() -> T? {
return list.last
}
typealias ObjectType = T
}
3. Use it with any Data Type:
var stackInt:GenericStack<Int> = GenericStack<Int>()
print(stackInt.push(value: 5))
print(stackInt.push(value: 7))
print(stackInt.elements)
var stackChar:GenericStack<Character> = GenericStack<Character>()
print(stackChar.push(value: "A"))
print(stackChar.push(value: "B"))
print(stackChar.elements)
var stackString:GenericStack<String> = GenericStack<String>()
print(stackString.push(value: "Abhi"))
print(stackString.push(value: "test"))
print(stackString.elements)
Video of execution and learning stack in swift : XcodePlaygroundWork