Shortens `anArray.count ?? 0` to `anArray.count` just like in ObjC

Optional+SupportsCount.swift

//
//  Optional+SupportsCount.swift
//
//  Created by John Scott on 02/03/2019.
//


/**
 This file contains a little syntactic sugar to help the Objective-C oldies.
 
 When calling `anArray.count` we often relied on ObjC to return `0` when `anArray`
 was `nil`. These days, in Swift, we're forced to write something like:
 
 ```
 anArray.count ?? 0
 ```
 
 :-(
 
 The following code allows us to go back to the old way, but **just** for `count`.
 */

import Foundation

protocol SupportsCount {
    var count: Int { get }
}

extension ContiguousArray: SupportsCount {}
extension ArraySlice: SupportsCount {}
extension Array: SupportsCount {}

extension Optional where Wrapped: SupportsCount {
    var count: Int { return self?.count ?? 0 }
}