I am currently in need of a performant bidirectional map. In Swift, a dictionary can be reversed, however, that will return a tuple of the types it is made of, not a counterpart dictionary.
Is there a library for that or does someone have ideas on how to address this issue?
Thanks
With Swift 4 you could easily make your own using a generic struct:
struct BidiMap<F:Hashable,T:Hashable>
{
private var _forward : [F:T]? = nil
private var _backward : [T:F]? = nil
var forward:[F:T]
{
mutating get
{
_forward = _forward ?? [F:T](uniqueKeysWithValues:_backward?.map{($1,$0)} ?? [] )
return _forward!
}
set { _forward = newValue; _backward = nil }
}
var backward:[T:F]
{
mutating get
{
_backward = _backward ?? [T:F](uniqueKeysWithValues:_forward?.map{($1,$0)} ?? [] )
return _backward!
}
set { _backward = newValue; _forward = nil }
}
init(_ dict:[F:T] = [:])
{ forward = dict }
init(_ values:[(F,T)])
{ forward = [F:T](uniqueKeysWithValues:values) }
subscript(_ key:T) -> F?
{ mutating get { return backward[key] } set{ backward[key] = newValue } }
subscript(_ key:F) -> T?
{ mutating get { return forward[key] } set{ forward[key] = newValue } }
subscript(to key:T) -> F?
{ mutating get { return backward[key] } set{ backward[key] = newValue } }
subscript(from key:F) -> T?
{ mutating get { return forward[key] } set{ forward[key] = newValue } }
var count:Int { return _forward?.count ?? _backward?.count ?? 0 }
}
var bd = BidiMap( [1:"A", 2:"B", 3:"C"] )
bd[1] // "A"
bd["B"] // 2
bd[4] = "D"
bd[to:"D"] // 4
bd[from:4] // "D"
var int2int = BidiMap( [1:2, 5:3] )
int2int[from:1] // 2
int2int[to:3] // 5
[EDIT] improved performance a bit by delaying rebuilding of mirror dictionary until it is actually referenced.
Related
Take this case of a type constrained class Parameter, wrapping a value of given type.
Parameter conforms to the AnyParameter so it can be passed anywhere in the app without knowing the type. Parameters can be displayed in value cells AnyValueCell
How would you do to observe the change without having to know the underlying value type? It would be nice to avoid the code repetition in the value cell updateObserver function
Could AnyPublisher can be used here and how?
import UIKit
import Combine
print("Hello Playground")
protocol AnyParameter {
var anyValue: Any { get }
func set(value: Any)
}
protocol ParameterProtocol: AnyParameter {
associatedtype ValueType
var value: ValueType { get }
func set(value: ValueType)
}
public class Parameter<T>: ParameterProtocol {
typealias ValueType = T
#Published var value: T
var anyValue: Any { value }
init(value: T) {
self.value = value
}
func set(value: Any) {
guard let value = value as? T else { return }
set(value: value)
}
func set(value: T) {
self.value = value
}
}
public class AnyValueCell {
var parameter: AnyParameter {
didSet {
updateObserver()
}
}
var observer: AnyCancellable?
init(parameter: AnyParameter) {
self.parameter = parameter
updateObserver()
}
func updateObserver() {
observer?.cancel()
// This is the point of the question - How to make this generic?
// ---->
if let p = parameter as? Parameter<Int> {
observer = p.$value.sink() { value in
print("Update Cell -> \(value)")
}
return
}
if let p = parameter as? Parameter<Double> {
observer = p.$value.sink() { value in
print("Update Cell -> \(value)")
}
return
}
if let p = parameter as? Parameter<Bool> {
observer = p.$value.sink() { value in
print("Update Cell -> \(value)")
}
return
}
// <----
print("Wrong param type")
}
}
let intParam = Parameter<Int>(value: 42)
let doubleParam = Parameter<Double>(value: 3.14)
let boolParam = Parameter<Bool>(value: false)
var params: [AnyParameter] = [intParam, doubleParam, boolParam]
print ("--> Init Cells")
let cells: [AnyValueCell] = params.map { AnyValueCell(parameter: $0) }
print ("--> Change values")
intParam.set(value: 21)
doubleParam.set(value: 1.618)
boolParam.set(value: true)
Result, as expected:
Hello Playground
--> Init Cells
Update Cell -> 42
Update Cell -> 3.14
Update Cell -> false
--> Change values
Update Cell -> 21
Update Cell -> 1.618
Update Cell -> true
Add an anyValuePublisher property. You can (and maybe should) add it to AnyParameter, or you can define it in a separate protocol like this:
protocol AnyParameterPublishing: AnyParameter {
var anyValuePublisher: AnyPublisher<Any, Never> { get }
}
extension Parameter: AnyParameterPublishing {
var anyValuePublisher: AnyPublisher<Any, Never> {
return $value.map { $0 as Any }.eraseToAnyPublisher()
}
}
Then you can use it like this:
class AnyValueCell {
// ...
func updateObserver() {
guard let publishing = (parameter as? AnyParameterPublishing) else {
print("Wrong param type")
return
}
observer = publishing.anyValuePublisher
.sink { print("Update Cell -> \($0)") }
}
}
Xcode 11.3, Swift 5.1.3
I am trying currently to create a custom property wrapper that allows me to link variables to a Firebase database. When doing this, to make it update the view, I at first tried to use the #ObservedObject #Bar var foo = []. But I get an error that multiple property wrappers are not supported. Next thing I tried to do, which would honestly be ideal, was try to make my custom property wrapper update the view itself upon being changed, just like #State and #ObservedObject. This both avoids needing to go down two layers to access the underlying values and avoid the use of nesting property wrappers. To do this, I checked the SwiftUI documentation and found out that they both implement the DynamicProperty protocol. I tried to use this too but failed because I need to be able to update the view (call update()) from within my Firebase database observers, which I cannot do since .update() is mutating.
Here is my current attempt at this:
import SwiftUI
import Firebase
import CodableFirebase
import Combine
#propertyWrapper
final class DatabaseBackedArray<Element>: ObservableObject where Element: Codable & Identifiable {
typealias ObserverHandle = UInt
typealias Action = RealtimeDatabase.Action
typealias Event = RealtimeDatabase.Event
private(set) var reference: DatabaseReference
private var currentValue: [Element]
private var childAddedObserverHandle: ObserverHandle?
private var childChangedObserverHandle: ObserverHandle?
private var childRemovedObserverHandle: ObserverHandle?
private var childAddedActions: [Action<[Element]>] = []
private var childChangedActions: [Action<[Element]>] = []
private var childRemovedActions: [Action<[Element]>] = []
init(wrappedValue: [Element], _ path: KeyPath<RealtimeDatabase, RealtimeDatabase>, events: Event = .all,
actions: [Action<[Element]>] = []) {
currentValue = wrappedValue
reference = RealtimeDatabase()[keyPath: path].reference
for action in actions {
if action.event.contains(.childAdded) {
childAddedActions.append(action)
}
if action.event.contains(.childChanged) {
childChangedActions.append(action)
}
if action.event.contains(.childRemoved) {
childRemovedActions.append(action)
}
}
if events.contains(.childAdded) {
childAddedObserverHandle = reference.observe(.childAdded) { snapshot in
guard let value = snapshot.value, let decodedValue = try? FirebaseDecoder().decode(Element.self, from: value) else {
fatalError("Could not decode value from Firebase.")
}
self.objectWillChange.send()
self.currentValue.append(decodedValue)
self.childAddedActions.forEach { $0.action(&self.currentValue) }
}
}
if events.contains(.childChanged) {
childChangedObserverHandle = reference.observe(.childChanged) { snapshot in
guard let value = snapshot.value, let decodedValue = try? FirebaseDecoder().decode(Element.self, from: value) else {
fatalError("Could not decode value from Firebase.")
}
guard let changeIndex = self.currentValue.firstIndex(where: { $0.id == decodedValue.id }) else {
return
}
self.objectWillChange.send()
self.currentValue[changeIndex] = decodedValue
self.childChangedActions.forEach { $0.action(&self.currentValue) }
}
}
if events.contains(.childRemoved) {
childRemovedObserverHandle = reference.observe(.childRemoved) { snapshot in
guard let value = snapshot.value, let decodedValue = try? FirebaseDecoder().decode(Element.self, from: value) else {
fatalError("Could not decode value from Firebase.")
}
self.objectWillChange.send()
self.currentValue.removeAll { $0.id == decodedValue.id }
self.childRemovedActions.forEach { $0.action(&self.currentValue) }
}
}
}
private func setValue(to value: [Element]) {
guard let encodedValue = try? FirebaseEncoder().encode(currentValue) else {
fatalError("Could not encode value to Firebase.")
}
reference.setValue(encodedValue)
}
var wrappedValue: [Element] {
get {
return currentValue
}
set {
self.objectWillChange.send()
setValue(to: newValue)
}
}
var projectedValue: Binding<[Element]> {
return Binding(get: {
return self.wrappedValue
}) { newValue in
self.wrappedValue = newValue
}
}
var hasActiveObserver: Bool {
return childAddedObserverHandle != nil || childChangedObserverHandle != nil || childRemovedObserverHandle != nil
}
var hasChildAddedObserver: Bool {
return childAddedObserverHandle != nil
}
var hasChildChangedObserver: Bool {
return childChangedObserverHandle != nil
}
var hasChildRemovedObserver: Bool {
return childRemovedObserverHandle != nil
}
func connectObservers(for event: Event) {
if event.contains(.childAdded) && childAddedObserverHandle == nil {
childAddedObserverHandle = reference.observe(.childAdded) { snapshot in
guard let value = snapshot.value, let decodedValue = try? FirebaseDecoder().decode(Element.self, from: value) else {
fatalError("Could not decode value from Firebase.")
}
self.objectWillChange.send()
self.currentValue.append(decodedValue)
self.childAddedActions.forEach { $0.action(&self.currentValue) }
}
}
if event.contains(.childChanged) && childChangedObserverHandle == nil {
childChangedObserverHandle = reference.observe(.childChanged) { snapshot in
guard let value = snapshot.value, let decodedValue = try? FirebaseDecoder().decode(Element.self, from: value) else {
fatalError("Could not decode value from Firebase.")
}
guard let changeIndex = self.currentValue.firstIndex(where: { $0.id == decodedValue.id }) else {
return
}
self.objectWillChange.send()
self.currentValue[changeIndex] = decodedValue
self.childChangedActions.forEach { $0.action(&self.currentValue) }
}
}
if event.contains(.childRemoved) && childRemovedObserverHandle == nil {
childRemovedObserverHandle = reference.observe(.childRemoved) { snapshot in
guard let value = snapshot.value, let decodedValue = try? FirebaseDecoder().decode(Element.self, from: value) else {
fatalError("Could not decode value from Firebase.")
}
self.objectWillChange.send()
self.currentValue.removeAll { $0.id == decodedValue.id }
self.childRemovedActions.forEach { $0.action(&self.currentValue) }
}
}
}
func removeObserver(for event: Event) {
if event.contains(.childAdded), let handle = childAddedObserverHandle {
reference.removeObserver(withHandle: handle)
self.childAddedObserverHandle = nil
}
if event.contains(.childChanged), let handle = childChangedObserverHandle {
reference.removeObserver(withHandle: handle)
self.childChangedObserverHandle = nil
}
if event.contains(.childRemoved), let handle = childRemovedObserverHandle {
reference.removeObserver(withHandle: handle)
self.childRemovedObserverHandle = nil
}
}
func removeAction(_ action: Action<[Element]>) {
if action.event.contains(.childAdded) {
childAddedActions.removeAll { $0.id == action.id }
}
if action.event.contains(.childChanged) {
childChangedActions.removeAll { $0.id == action.id }
}
if action.event.contains(.childRemoved) {
childRemovedActions.removeAll { $0.id == action.id }
}
}
func removeAllActions(for event: Event) {
if event.contains(.childAdded) {
childAddedActions = []
}
if event.contains(.childChanged) {
childChangedActions = []
}
if event.contains(.childRemoved) {
childRemovedActions = []
}
}
}
struct School: Codable, Identifiable {
/// The unique id of the school.
var id: String
/// The name of the school.
var name: String
/// The city of the school.
var city: String
/// The province of the school.
var province: String
/// Email domains for student emails from the school.
var domains: [String]
}
#dynamicMemberLookup
struct RealtimeDatabase {
private var path: [String]
var reference: DatabaseReference {
var ref = Database.database().reference()
for component in path {
ref = ref.child(component)
}
return ref
}
init(previous: Self? = nil, child: String? = nil) {
if let previous = previous {
path = previous.path
} else {
path = []
}
if let child = child {
path.append(child)
}
}
static subscript(dynamicMember member: String) -> Self {
return Self(child: member)
}
subscript(dynamicMember member: String) -> Self {
return Self(child: member)
}
static subscript(dynamicMember keyPath: KeyPath<Self, Self>) -> Self {
return Self()[keyPath: keyPath]
}
static let reference = Database.database().reference()
struct Event: OptionSet, Hashable {
let rawValue: UInt
static let childAdded = Event(rawValue: 1 << 0)
static let childChanged = Event(rawValue: 1 << 1)
static let childRemoved = Event(rawValue: 1 << 2)
static let all: Event = [.childAdded, .childChanged, .childRemoved]
static let constructive: Event = [.childAdded, .childChanged]
static let destructive: Event = .childRemoved
}
struct Action<Value>: Identifiable {
let id = UUID()
let event: Event
let action: (inout Value) -> Void
private init(on event: Event, perform action: #escaping (inout Value) -> Void) {
self.event = event
self.action = action
}
static func on<Value>(_ event: RealtimeDatabase.Event, perform action: #escaping (inout Value) -> Void) -> Action<Value> {
return Action<Value>(on: event, perform: action)
}
}
}
Usage example:
struct ContentView: View {
#DatabaseBackedArray(\.schools, events: .all, actions: [.on(.constructive) { $0.sort { $0.name < $1.name } }])
var schools: [School] = []
var body: some View {
Text("School: ").bold() +
Text(schools.isEmpty ? "Loading..." : schools.first!.name)
}
}
When I try to use this though, the view never updates with the value from Firebase even though I am positive that the .childAdded observer is being called.
One of my attempts at fixing this was to store all of these variables in a singleton that itself conforms to ObservableObject. This solution is also ideal as it allows the variables being observed to be shared throughout my application, preventing multiples instances of the same date and allowing for a single source of truth. Unfortunately, this too did not update the view with the fetched value of currentValue.
class Session: ObservableObject {
#DatabaseBackedArray(\.schools, events: .all, actions: [.on(.constructive) { $0.sort { $0.name < $1.name } }])
var schools: [School] = []
private init() {
//Send `objectWillChange` when `schools` property changes
_schools.objectWillChange.sink {
self.objectWillChange.send()
}
}
static let current = Session()
}
struct ContentView: View {
#ObservedObject
var session = Session.current
var body: some View {
Text("School: ").bold() +
Text(session.schools.isEmpty ? "Loading..." : session.schools.first!.name)
}
}
Is there any way to make a custom property wrapper that also updates a view in SwiftUI?
Making use of the DynamicProperty protocol we can easily trigger view updates by making use of SwiftUI's existing property wrappers. (DynamicProperty tells SwiftUI to look for these within our type)
#propertyWrapper
struct OurPropertyWrapper: DynamicProperty {
// A state object that we notify of updates
#StateObject private var updater = Updater()
var wrappedValue: T {
get {
// Your getter code here
}
nonmutating set {
// Tell SwiftUI we're going to change something
updater.notifyUpdate()
// Your setter code here
}
}
class Updater: ObservableObject {
func notifyUpdate() {
objectWillChange.send()
}
}
}
The solution to this is to make a minor tweak to the solution of the singleton. Credits to #user1046037 for pointing this out to me. The problem with the singleton fix mentioned in the original post, is that it does not retain the canceller for the sink in the initializer. Here is the correct code:
class Session: ObservableObject {
#DatabaseBackedArray(\.schools, events: .all, actions: [.on(.constructive) { $0.sort { $0.name < $1.name } }])
var schools: [School] = []
private var cancellers = [AnyCancellable]()
private init() {
_schools.objectWillChange.sink {
self.objectWillChange.send()
}.assign(to: &cancellers)
}
static let current = Session()
}
Consider the following:
struct MiniString {
private(set) var value: String
init(_ value: String) {
if value.count < 17 {
self.value = value
} else {
selfDeleteSomehow()
}
}
}
Elsewhere this could be instantiated thus:
var ms: MiniString? = MiniString("This string is too long to be accepted")
print(ms) // prints 'nil'
Context: my specific use-case is for a func declaration in a protocol that would return a Double between 0.0 and 1.0, but no higher or lower, something like:
protocol DoubleBetweenZeroAndOneProtocol {
func getResult() -> DoubleBetweenZeroAndOne
}
You could use a failable initializer:
struct MiniString {
var value: String { return value_ }
private let value_: String
init?(_ seedValue: String) {
if seedValue.count < 17 {
value_ = seedValue
} else {
return nil
}
}
}
I have written the following extension for Collection in Swift that returns a new Collection of every other element from a starting index.
extension Collection {
func everyOtherElement(from theIndex: Int = 0) -> [Element] {
if theIndex >= self.count { return self as! [Element] }
let start = self.index(startIndex, offsetBy: theIndex)
let end = self.endIndex
var everyOther = [Element]()
var iter = start
while iter != end {
everyOther.append(self[iter])
let next = index(after: iter)
if next == end { break }
iter = index(after: next)
}
return everyOther
}
}
There are probably ways to improve the code but my issue is when the Collection is a Dictionary. The extension works but returns an Array of Tuples [(key: key, value: value)]
I would like the extension to return a Dictionary.
I have tried Dictionary(uniqueKeysWithValuesMethod) which works fine once applied to the return of the everyOtherElement method but I can't seem to find a way to make it so directly.
var myDictionary = ["EN" : "Cheers", "SV" : "Skåll", "ES" : "Salud" ].everyOtherElement()
// returns [(key: "EN", value: "Cheers"),(key: "ES", value: "Salud")]
Dictionary(uniqueKeysWithValues: myDictionary.map { ($0.key, $0.value)})
// returns ["EN" : "Cheers", "ES" : "Salud" ]
Thanks for your help!
As other have mentioned a Dictionary is an unordered collection. If you would like to return a Dictionary you can simply extend dictionary and filter every other element. Note that there is no guarantee that the dictionary will keep the order that the key value pairs were enterer. That being said you can accomplish what you want as follow:
extension Dictionary {
var everyOtherElements: Dictionary {
var bool = true
return filter { _ in
defer { bool = !bool }
return bool
}
}
}
let dict = ["EN" : "Cheers", "SV" : "Skåll", "ES" : "Salud" ]
// returns [(key: "EN",
let everyOtherElements = dict.everyOtherElements // ["ES": "Salud", "SV": "Skåll"]
Regarding your comment
I understand from your reply that I can't extend all collection with
the same code, I need to break it down per type?
You don't need to extend every single element type, you can for instance extend RangeReplaceableCollection protocol and return Self which will englobe Strings as well:
extension RangeReplaceableCollection {
mutating func removeEvenIndexElements() {
var bool = true
removeAll { _ in
defer { bool = !bool }
return bool
}
}
mutating func removeOddIndexElements() {
var bool = false
removeAll { _ in
defer { bool = !bool }
return bool
}
}
func evenIndexElements() -> Self {
var bool = true
return filter { _ in
defer { bool = !bool }
return bool
}
}
func oddIndexElements() -> Self {
var bool = false
return filter { _ in
defer { bool = !bool }
return bool
}
}
}
var alphabet = "abcdefghijklmnopqrstuvwxyz"
alphabet.removeEvenIndexElements()
alphabet // "bdfhjlnprtvxz"
var arr = [1,2,3,4,5,6,7,8,9,0]
arr.removeOddIndexElements()
arr // [1, 3, 5, 7, 9]
Is there a standard swift class that is a Dictionary, but keeps keys in insertion-order like Java's LinkedHashMap? If not, how would one be implemented?
Didn't know of one and it was an interesting problem to solve (already put it in my standard library of stuff) Mostly it's just a matter of maintaining a dictionary and an array of the keys side-by-side. But standard operations like for (key, value) in od and for key in od.keys will iterate in insertion order rather than a semi random fashion.
// OrderedDictionary behaves like a Dictionary except that it maintains
// the insertion order of the keys, so iteration order matches insertion
// order.
struct OrderedDictionary<KeyType:Hashable, ValueType> {
private var _dictionary:Dictionary<KeyType, ValueType>
private var _keys:Array<KeyType>
init() {
_dictionary = [:]
_keys = []
}
init(minimumCapacity:Int) {
_dictionary = Dictionary<KeyType, ValueType>(minimumCapacity:minimumCapacity)
_keys = Array<KeyType>()
}
init(_ dictionary:Dictionary<KeyType, ValueType>) {
_dictionary = dictionary
_keys = map(dictionary.keys) { $0 }
}
subscript(key:KeyType) -> ValueType? {
get {
return _dictionary[key]
}
set {
if newValue == nil {
self.removeValueForKey(key)
}
else {
self.updateValue(newValue!, forKey: key)
}
}
}
mutating func updateValue(value:ValueType, forKey key:KeyType) -> ValueType? {
let oldValue = _dictionary.updateValue(value, forKey: key)
if oldValue == nil {
_keys.append(key)
}
return oldValue
}
mutating func removeValueForKey(key:KeyType) {
_keys = _keys.filter { $0 != key }
_dictionary.removeValueForKey(key)
}
mutating func removeAll(keepCapacity:Int) {
_keys = []
_dictionary = Dictionary<KeyType,ValueType>(minimumCapacity: keepCapacity)
}
var count: Int { get { return _dictionary.count } }
// keys isn't lazy evaluated because it's just an array anyway
var keys:[KeyType] { get { return _keys } }
// values is lazy evaluated because of the dictionary lookup and creating a new array
var values:GeneratorOf<ValueType> {
get {
var index = 0
return GeneratorOf<ValueType> {
if index >= self._keys.count {
return nil
}
else {
let key = self._keys[index]
index++
return self._dictionary[key]
}
}
}
}
}
extension OrderedDictionary : SequenceType {
func generate() -> GeneratorOf<(KeyType, ValueType)> {
var index = 0
return GeneratorOf<(KeyType, ValueType)> {
if index >= self._keys.count {
return nil
}
else {
let key = self._keys[index]
index++
return (key, self._dictionary[key]!)
}
}
}
}
func ==<Key: Equatable, Value: Equatable>(lhs: OrderedDictionary<Key, Value>, rhs: OrderedDictionary<Key, Value>) -> Bool {
return lhs._keys == rhs._keys && lhs._dictionary == rhs._dictionary
}
func !=<Key: Equatable, Value: Equatable>(lhs: OrderedDictionary<Key, Value>, rhs: OrderedDictionary<Key, Value>) -> Bool {
return lhs._keys != rhs._keys || lhs._dictionary != rhs._dictionary
}
Swift 5 version:
// OrderedDictionary behaves like a Dictionary except that it maintains
// the insertion order of the keys, so iteration order matches insertion
// order.
struct OrderedDictionary<KeyType: Hashable, ValueType> {
private var _dictionary: Dictionary<KeyType, ValueType>
private var _keys: Array<KeyType>
init() {
_dictionary = [:]
_keys = []
}
init(minimumCapacity: Int) {
_dictionary = Dictionary<KeyType, ValueType>(minimumCapacity: minimumCapacity)
_keys = Array<KeyType>()
}
init(_ dictionary: Dictionary<KeyType, ValueType>) {
_dictionary = dictionary
_keys = dictionary.keys.map { $0 }
}
subscript(key: KeyType) -> ValueType? {
get {
_dictionary[key]
}
set {
if newValue == nil {
self.removeValueForKey(key: key)
} else {
_ = self.updateValue(value: newValue!, forKey: key)
}
}
}
mutating func updateValue(value: ValueType, forKey key: KeyType) -> ValueType? {
let oldValue = _dictionary.updateValue(value, forKey: key)
if oldValue == nil {
_keys.append(key)
}
return oldValue
}
mutating func removeValueForKey(key: KeyType) {
_keys = _keys.filter {
$0 != key
}
_dictionary.removeValue(forKey: key)
}
mutating func removeAll(keepCapacity: Int) {
_keys = []
_dictionary = Dictionary<KeyType, ValueType>(minimumCapacity: keepCapacity)
}
var count: Int {
get {
_dictionary.count
}
}
// keys isn't lazy evaluated because it's just an array anyway
var keys: [KeyType] {
get {
_keys
}
}
var values: Array<ValueType> {
get {
_keys.map { _dictionary[$0]! }
}
}
static func ==<Key: Equatable, Value: Equatable>(lhs: OrderedDictionary<Key, Value>, rhs: OrderedDictionary<Key, Value>) -> Bool {
lhs._keys == rhs._keys && lhs._dictionary == rhs._dictionary
}
static func !=<Key: Equatable, Value: Equatable>(lhs: OrderedDictionary<Key, Value>, rhs: OrderedDictionary<Key, Value>) -> Bool {
lhs._keys != rhs._keys || lhs._dictionary != rhs._dictionary
}
}
extension OrderedDictionary: Sequence {
public func makeIterator() -> OrderedDictionaryIterator<KeyType, ValueType> {
OrderedDictionaryIterator<KeyType, ValueType>(sequence: _dictionary, keys: _keys, current: 0)
}
}
struct OrderedDictionaryIterator<KeyType: Hashable, ValueType>: IteratorProtocol {
let sequence: Dictionary<KeyType, ValueType>
let keys: Array<KeyType>
var current = 0
mutating func next() -> (KeyType, ValueType)? {
defer { current += 1 }
guard sequence.count > current else {
return nil
}
let key = keys[current]
guard let value = sequence[key] else {
return nil
}
return (key, value)
}
}
I didn't found way to make values 'lazy'.. need more research