I am implementing HasDelegate protocol to the IWDeviceManager.
In all the posts which I have read, no one has wrote getter & setter for this public var delegate property.
The compiler is explicitly asking me to write getter & setter for public var delegate. Why it's required in my case?
I tried writing but my code crashes when I try to get or set the delegate.
How do I solve this issue?
I have shared the code below
extension IWDeviceManager: HasDelegate {
public typealias Delegate = IWDeviceManagerDelegate
// Compiler explicitly asks to write getter and setter for this.
public var delegate: IWDeviceManagerDelegate? {
get { // Crashes here
return IWDeviceManager.shared()?.delegate
}
set(newValue) { // crashes here
IWDeviceManager.shared()?.delegate = newValue
}
}
}
Below is interface for IWDeviceManager
open class IWDeviceManager : NSObject {
weak open var delegate: IWDeviceManagerDelegate!
open class func shared() -> Self!
open func initMgr()
open func initMgr(with config: IWDeviceManagerConfig!)
}
Instead of using HasDelegate try this:
class IWDeviceManagerDelegateProxy
: DelegateProxy<IWDeviceManager, IWDeviceManagerDelegate>
, DelegateProxyType
, IWDeviceManagerDelegate {
init(parentObject: IWDeviceManager) {
super.init(parentObject: parentObject, delegateProxy: IWDeviceManagerDelegateProxy.self)
}
static func currentDelegate(for object: IWDeviceManager) -> Delegate? {
return object.delegate
}
static func setCurrentDelegate(_ delegate: IWDeviceManagerDelegate?, to object: IWDeviceManager) {
object.delegate = delegate
}
static func registerKnownImplementations() {
self.register { IWDeviceManagerDelegateProxy(parentObject: $0) }
}
}
I am using Parse and have created a subclass of PFObject. When creating objects it makes things much easier. Once objects are created, I am experimenting with querying the database and accessing the custom properties I created. What I am finding is that I cannot use dot notation to access the properties when I am working the the PFObjects returned from the query. Is this normal?
Here is subclass I created.
import Foundation
import UIKit
import Parse
class MessagePFObject: PFObject
{
#NSManaged var messageSender : String
#NSManaged var messageReceiver : String
#NSManaged var messageMessage : String
#NSManaged var messageSeen : Bool
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
// Custom Query method.
override class func query() -> PFQuery?
{
let query = PFQuery(className: MessagePFObject.parseClassName())
query.includeKey("user")
query.orderByDescending("createdAt")
return query
}
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
init(messageSenderInput: String?, messageReceiverInput: String?, messageMessageInput: String?)
{
super.init()
self.messageSender = messageSenderInput!
self.messageReceiver = messageReceiverInput!
self.messageMessage = messageMessageInput!
self.messageSeen = false
}
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
override init()
{
super.init()
}
}
//++++++++++++++++++++++++++++++++++++ EXTENSION +++++++++++++++++++++++++++++++++++++++++++++++++++
extension MessagePFObject : PFSubclassing
{
class func parseClassName() -> String
{
return "MessagePFObject"
}
//+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
override class func initialize()
{
var onceToken: dispatch_once_t = 0
dispatch_once(&onceToken) {
self.registerSubclass()
}
}
}
Here is my query and what I am required to do to access the properties. createdAt, updatedAt, etc are all available with dot notation but none of my custom properties are. You can see I access messageSeen with element.objectForKey("messageSeen").
let predicate = NSPredicate(format: "messageSender == %# OR messageReceiver == %#", self.currentUser!.username!, self.currentUser!.username!)
let query = messagePFObject.queryWithPredicate(predicate)
query!.findObjectsInBackgroundWithBlock ({ (objects, error) -> Void in
if error == nil && objects!.count > 0
{
for element in objects!
{
print(element)
print(element.parseClassName)
print(element.objectId)
print(element.createdAt)
print(element.updatedAt)
print(element.objectForKey("messageSeen"))
}
}
else if error != nil
{
print(error)
}
})
If this is normal then that is fine. I just want to make sure I am not missing something.
Take care,
Jon
Your object subclass has to implement the PFSubclassing protocol and you need to call MessagePFObject.registerSubclass() in your app delegate.
The parse documentation is very good : https://parse.com/docs/ios/guide#objects-subclasses
I have a class which will perform a search. Once complete I want the search class to pass back the results to which ever instance (of another class) started the search. My thinking was to pass a reference to the class which instantiates the search class and use that reference to call a function. Here's a basic example of what I'm trying to do. How can I get this to work, or is there another/better way?
Search Class (I've tried AnyObject and UITableViewContoller):
class SearchClass : NSObject, NSURLConnectionDelegate, NSURLConnectionDataDelegate {
var callingClass : AnyObject? = nil //To store reference to the "other" class
var searchResults : [[String : AnyObject]]? = nil
init(callingClass: AnyObject) { //I don't know the name of the ViewController class which will instantiates this as it will be called by several different classes
self.callingClass = callingClass
}
func startSearch(searchString: String) {
//NSURLConnection etc
}
func connectionDidFinishLoading(connection: NSURLConnection) {
//more code
searchResults = ...
callingClass!.searchCompleted(searchResults) //Pass the search results back to the class instance which started the search
}
}
Other Classes:
class RandomViewController : UITableViewController {
//The casting on the next line fails
let Searcher = SearchClass(callingClass: self as! UITableViewController) //OR AnyObject
func randomFunction() {
searcher.startSearch("search query")
}
func searchComplete(searchResults: [[String : AnyObject]]) {
self.searchResults = searchResults
tableView.reloadData()
}
}
You can add a closure parameter to your startSearch function in your search class:
typealias SearchResultHandler = (result: [String : AnyObject]) -> ()
func startSearch(query: String, resultHandler: SearchResultHandler) {
// send the search request and in the completion handler of the request call your result handler:
resultHandler(result: searchResult)
}
Which you would then call from any class:
let searcher = SearchClass()
searcher.startSearch("query") { (result) -> () in
self.searchResults = results
tableView.reloadData()
}
You can use generics when you don't know what the class is going to be:
https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Generics.html
However....
This seems like something that you should use protocol / delegates for.
// NOTE: weak references must be class type
protocol SearchClassDelegate: class {
func searchComplete(results: [[String: AnyObject]?])
}
// This is where you define T as the generic class
class SearchClass {
weak var delegate: SearchClassDelegate? // This is your "callingClass"
// NOTE: make sure it's weak
// ...
func connectionDidFinishLoading() {
// ...
self.delegate?.searchComplete(results)
}
}
// Set to the delegate
class ViewController: UIViewController, SearchClassDelegate {
// ...
// Make sure you set the delegate
// Here is where you implement this function
func searchComplete(results: [[String : AnyObject]?]) {
// Do whatever
// ...reloadData() etc.
}
}
I have created a wrapper class for storing a weak object reference, and then. I want to remove objects that have not a valid reference inside.
class Weak<T: AnyObject> {
weak var value : T?
init (value: T) {
self.value = value
}
}
protocol CSLocationServicesDelegate : class{
}
class conformance : CSLocationServicesDelegate{
}
class Dispatcher{
var dispatchArray = Array<Weak<CSLocationServicesDelegate>>()
func add( delegate : CSLocationServicesDelegate!){
dispatchArray.append(Weak(value: delegate));
}
func remove(obj : CSLocationServicesDelegate!){
dispatchArray.filter { (weakRef : Weak<CSLocationServicesDelegate>) -> Bool in
return weakRef.value != nil; //change this line to "return true" and it works!!!
}
}
}
However Xcode compilation fails with an error being reported, which shows absolutely no specific error. I suspect that I am using the language in such a false manner, that Xcode cannot figure out what I want to do. If I change the line (in the comments) to what the comment says, it works.
Can anyone help me in achieving what I want?
I don't see anything wrong with your code, but the compiler is crashing when compiling it. That should definitely be reported to Apple.
One workaround for this seems to be to simply declare Weak as a struct instead of a class. This compiles just fine:
struct Weak<T: AnyObject> {
weak var value : T?
init (value: T) {
self.value = value
}
}
protocol CSLocationServicesDelegate : class{
}
class conformance : CSLocationServicesDelegate{
}
class Dispatcher{
var dispatchArray = Array<Weak<CSLocationServicesDelegate>>()
func add( delegate : CSLocationServicesDelegate!){
dispatchArray.append(Weak(value: delegate));
}
func remove(obj : CSLocationServicesDelegate!){
dispatchArray.filter { (weakRef : Weak<CSLocationServicesDelegate>) -> Bool in
return weakRef.value != nil
}
}
}
I begin my project with a split view controller as initial view controller and start it automatically from storyboard.
Generally, an app with this UI have one and only one split view controller as root, so I create a static variable in the subclass and set it when initialisation was done.
So I want try this behaviour with swift.
I read the Swift programming language guide book on iBook about Type properties (with static and class keyword) and trying a piece of code to the job:
import UIKit
class SplitViewController: UISplitViewController {
class func sharedInstance() -> SplitViewController {
return SplitViewController.instance
}
class let instance: SplitViewController = nil
init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
self.initialization()
}
init(coder aDecoder: NSCoder!) {
super.init(coder: aDecoder);
self.initialization()
}
func initialization() {
SplitViewController.instance = self;
}
}
but I figured out when Xcode say the class keyword for type properties wasn't supported yet.
Did you have a solution to do this ?
Embedding a struct can work just fine as a workaround:
class SomeClass
{
// class var classVariable: Int = 0
// "Class variables not yet supported." Weird.
// Workaround:
private struct SubStruct { static var staticVariable: Int = 0 }
class var workaroundClassVariable: Int
{
get { return SubStruct.staticVariable }
set { SubStruct.staticVariable = newValue }
}
}
The SomeClass.workaroundClassVariable computed type property can then be used as if it were a stored type property.
Swift now has support for static variables in classes. This is not exactly the same as a class variable (because they aren't inherited by subclasses), but it gets you pretty close:
class X {
static let y: Int = 4
static var x: Int = 4
}
println(X.x)
println(X.y)
X.x = 5
println(X.x)
It seems to be possible to declare variables with static storage duration in file scope (as in C):
var sharedInstance: SplitViewController? = nil
class SplitViewController: UISplitViewController {
....
func initialization() {
sharedInstance = self
}
}
My preferred method is to just use a private file scope var outside of the class and then implement class/static getters and setters:
private var _classVar: Int = 0;
class SomeClass
{
public class var classVar: Int
{
get { return _classVar }
set { _classVar = newValue }
}
}
As of Swift 1.2 (available with Xcode 6.3b1 and onwards), static class properties and methods are supported.
class SomeClass
{
static var someVariable: Int = 0
}
Using a dispatch_once singleton model in Swift
Seems to be the best answer so far, avoiding the use of a global variable.
A solution enough similar than var in file scope but more customisable and near singleton is to use a struct which support static var as property of class
struct PersonSharedData {
static var backstore = ""
var data: String {
get { return PersonSharedData.backstore }
set { PersonSharedData.backstore = newValue }
}
}
class Person {
var shared=PersonSharedData() //<< pseudo class var
var family: String {
get { return shared.data }
set { shared.data=newValue }
}
var firstname = ""
var lastname = ""
var sexe: Sexe = .Unknown
}
Ok, with the solution of Nikolai that do the work. I post my changes in this thread for information
var instance: SplitViewController? = nil
class SplitViewController: UISplitViewController {
class func sharedInstance() -> SplitViewController? {
return instance;
}
init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
self.initialization()
}
init(coder aDecoder: NSCoder!) {
super.init(coder: aDecoder);
self.initialization()
}
func initialization() {
instance = self
}
}
and for example, in my appDelegate, I can access this static method like this
SplitViewController.sharedInstance()!.presentsWithGesture = false
The wording in the error heavily implies this will be a language feature in the future.
You may want to resort temporarily to declaring a property variable in the Application Delegate and retrieve it from there. Not ideal, definitely an anti-pattern, but would give you a central place to retrieve the UISplitViewController when needed.
You have to wrap the class variables inside an inner struct variable
class Store{
var name:String
var address:String
var lat:Int
var long:Int
init(name:String, address:String, lat:Int, long:Int){
self.name = name
self.address = address
self.lat = lat
self.long=long
}
private struct FACTORY_INITIALIZED_FLAG { static var initialized: Bool = false
static var myStoreList:[Store]?
static func getMyStoreList()->[Store]{
if !initialized{
println("INITIALIZING")
myStoreList = [
Store(name: "Walmart", address: "abcd", lat: 10, long: 20),
Store(name: "JCPenny", address: "kjfnv", lat: 23, long: 34)
]
initialized = true
}
return myStoreList!
}
}
}
var a = Store.FACTORY_INITIALIZED_FLAG.getMyStoreList()
var b = Store.FACTORY_INITIALIZED_FLAG.getMyStoreList()
// only prints INITIALIZING once
Try this:
class var instance: SplitViewController {
return nil
}
It is called Type Property in Swift.
You define type properties with the static keyword. For computed type properties for class types, you can use the class keyword instead to allow subclasses to override the superclass’s implementation. The example below shows the syntax for stored and computed type properties:
struct SomeStructure {
static var storedTypeProperty = "Some value."
static var computedTypeProperty: Int {
return 1
}
}
enum SomeEnumeration {
static var storedTypeProperty = "Some value."
static var computedTypeProperty: Int {
return 6
}
}
class SomeClass {
static var storedTypeProperty = "Some value."
static var computedTypeProperty: Int {
return 27
}
class var overrideableComputedTypeProperty: Int {
return 107
}
}
Read more at link below,
https://developer.apple.com/library/ios/documentation/Swift/Conceptual/Swift_Programming_Language/Properties.html#//apple_ref/doc/uid/TP40014097-CH14-ID254