Synchronized Map and Array

README.md

Synchronized Map and Array

Dispatch is often used to protect a property when operating with concurrent behavior. A DispatchQueue can be used to ensure that a property is protected by using the sync function as demonstrated in the sample code below.

SynchronizedArray.swift

import Foundation

class SynchronizedArray<Value> {
    private let queue = DispatchQueue(label: "SynchronizedArray")
    private var array = [Value]()

    func find(at index: Int) -> Value? {
        return queue.sync {
            guard index < array.count else {
                return nil
            }
            return array[index]
        }
    }

    func add(item: Value) {
        queue.sync {
            array.append(item)
        }
    }

    func remove(at index: Int) {
        queue.sync {
            array.remove(at: index)
        }
    }
}

SynchronizedMap.swift

import Foundation

class SynchronizedMap<Key, Value> where Key : Hashable {
    private let queue = DispatchQueue(label: "SynchronizedMap")
    private var map = [Key:Value]()

    func find(key: Key) -> Value? {
        return queue.sync {
            return map[key]
        }
    }

    func add(key: Key, item: Value) {
        queue.sync {
            map[key] = item
        }
    }

    func remove(key: Key) {
        queue.sync {
            map[key] = nil
        }
    }
}

Usage.swift

struct Person {
    let name: String
}

extension Person: CustomStringConvertible {
    var description: String {
        return name
    }
}

var peopleMap = SynchronizedMap<String, Person>()

peopleMap.add(key: "Tim", item: Person(name: "Tim Cook"))
peopleMap.add(key: "Jony", item: Person(name: "Jony Ive"))
peopleMap.add(key: "Lisa", item: Person(name: "Lisa Jackson"))

peopleMap.find(key: "Tim")
peopleMap.find(key: "Jony")
peopleMap.find(key: "Eddy")
peopleMap.find(key: "Lisa")

var peopleArray = SynchronizedArray<Person>()

peopleArray.add(item: Person(name: "Tim Cook"))
peopleArray.add(item: Person(name: "Jony Ive"))
peopleArray.add(item: Person(name: "Lisa Jackson"))

peopleArray.find(at: 0)
peopleArray.find(at: 1)
peopleArray.find(at: 3)
peopleArray.find(at: 2)