Swift Array next and previous Items made easier.

BidirectionalCollection.swift

//
//  BidirectionalCollection.swift
//
//  Created by Kellen Styler
//


import Foundation


extension BidirectionalCollection where Iterator.Element: Equatable {
    typealias Element = Self.Iterator.Element
    
    func nextItem(withItem item: Element) -> Element? {
        guard let itemIndex = index(of: item) else { return nil }
        
        let nextIndex = index(after: itemIndex)
        guard nextIndex != endIndex else { return nil }

        return self[nextIndex]
    }
    
    func previousItem(withItem item: Element) -> Element? {
        guard let itemIndex = index(of: item) else { return nil }
        guard itemIndex != startIndex else { return nil }
        
        return self[index(before: itemIndex)]
    }
}