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iOS Generics in Swift Generic Types Creating a Generic Type

Bryce Vernon
Bryce Vernon
3,936 Points

Generics Code Challenge Task 5 of 5

I'm stuck on the very last task of the code challenge. Any help would be appreciated!

Add a second function named dequeue, that takes no parameters, and returns an optional Element. Since a queue follows a first in, first out policy, dequeue returns the element that was added first. If the queue is empty, return nil For example, given the queue: [1,4,9,7], calling dequeue returns 1, and the resulting queue is [4,9,7]. Note: Dequeue removes the first element from the array

generics.swift
struct Queue<Element> {
    var array = [Element]()
    var isEmpty: Bool {
        if array.isEmpty {
            return true
        } else {
            return false
        }
    }

    var count: Int {
        return array.count
    }

    mutating func enqueue(_ item: Element) {
        self.array.append(item)
    }

    mutating func dequeue() -> Element? {
        if self.array.isEmpty == false {
            self.array.remove(at: 0)
            return self.array[0]
        } else {
            return nil
        }

    }
}

3 Answers

Bryce Vernon
Bryce Vernon
3,936 Points

Ah I found the solution. Super simple since I read that the remove(at: Int) actually returns the removed item. So, I simply adjusted the code to reflect it.

struct Queue<Element> {
    var array = [Element]()
    var isEmpty: Bool {
        if array.isEmpty {
            return true
        } else {
            return false
        }
    }

    var count: Int {
        return array.count
    }

    mutating func enqueue(_ item: Element) {
        self.array.append(item)
    }

    mutating func dequeue() -> Element? {
        if self.array.isEmpty == false {
            return self.array.remove(at: 0)
        } else {
            return nil
        }

    }
}

Bryce Vernon's answer is correct :heavy_check_mark:

I'm adding an alternative solution below with a (very) slightly different implementation of the dequeue() instance method just for reference / for anyone curious (a.k.a., for when I have to come back to this six months from now):

struct Queue<Element> {
    var array: [Element] = []

    var isEmpty: Bool {
        if array.isEmpty {
            return true
        } else {
            return false
        }
    }

    var count: Int {
        return array.count
    }

    mutating func enqueue(_ newItem: Element) {
        array.append(newItem)
    }

    mutating func dequeue() -> Element? {
        if array.isEmpty == false {
            return array.removeFirst()
        } else {
            return nil
        }
    }
}
Stephen Wall
PLUS
Stephen Wall
Courses Plus Student 27,294 Points

I like your's Bryce, here's a cleaner version yet.

mutating func dequeue() -> Element? {
        if array.isEmpty {
            return nil
        }
        return array.removeFirst()
    }