Weak reference

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	<string>let alertController = UIAlertController(title: &lt;#T##String?#&gt;, message: &lt;#T##String?#&gt;, preferredStyle: &lt;#T##UIAlertController.Style#&gt;)
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let cancelAction = UIAlertAction(title: &lt;#T##String?#&gt;, style: .cancel, handler: nil)

alertController.addAction(firstAction)
alertController.addAction(cancelAction)
present(alertController, animated: true)</string>
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@IBAction func doSomething()
@IBAction func doSomething(sender: UIButton)
@IBAction func doSomething(sender: UIButton, forEvent event: UIEvent)

[[NSProcessInfo processInfo] operatingSystemVersion]

override func viewDidLoad() {
    super.viewDidLoad()
    // Swift block syntax (iOS 10+)
    let timer = Timer(timeInterval: 0.4, repeats: true) { _ in print("Done!") }
    // Swift >=3 selector syntax
    let timer = Timer.scheduledTimer(timeInterval: 0.4, target: self, selector: #selector(self.update), userInfo: nil, repeats: true)
    // Swift 2.2 selector syntax
    let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: #selector(MyClass.update), userInfo: nil, repeats: true)
    // Swift <2.2 selector syntax
    let timer = NSTimer.scheduledTimerWithTimeInterval(0.4, target: self, selector: "update", userInfo: nil, repeats: true)
}

// must be internal or public. 
@objc func update() {
    // Something cool
}

//'weak' must not be applied to non-class-bound 'any ListNotesDelegate'; consider adding a protocol conformance that has a class bound

//Whenever we want to create a weak reference the parent of object must conform to a class like AnyObject or UILabel etc.

//Example - 1

@IBOutlet weak private var titleLbl: UILabel!  //Here UILabel is a class
  
//Example - 2

protocol ListNotesDelegate {
    func refreshNotes()
    func deleteNote(with id: UUID)
}  

var delegate: ListNotesDelegate?  //You cannot assign this as weak var 
  
//To define it as weak -

protocol ListNotesDelegate:AnyObject {//Here AnyObject is a type alias for multiple classes
    func refreshNotes()
    func deleteNote(with id: UUID)
}  

weak var delegate: ListNotesDelegate?

// Preferred status bar style lightContent to use on dark background.
// Swift 3
override var preferredStatusBarStyle: UIStatusBarStyle {
    return .lightContent
}

// MARK: - Properties

// MARK: - IBOutlets

// MARK: - Life cycle

// MARK: - Set up

// MARK: - IBActions

// MARK: - Navigation

// MARK: - Network Manager calls

// MARK: - Extensions

import UIKit

extension UITableView {
    
    func dequeueReusableCell<T: UITableViewCell>() -> T {
        return dequeueReusableCell(withIdentifier: NSStringFromClass(T.self)) as! T
    }
}

//using: let cell: ExampleTableViewCell = tableView.dequeueReusableCell()

#include <iostream>
#include "unordered_set"
#include "basicActions.h"
using namespace std;

void createLoop(Node *head)
{
    Node *p = head;

    while (p->next != nullptr)
    {
        p = p->next;
    }
    p->next = head;
    return;
}

bool detectLoop(Node *head)
{
    unordered_set<Node *> s;
    Node *p = head;

    while (p != nullptr)
    {
        if (s.find(p) != s.end())
            return true;

        s.insert(p);
        p = p->next;
    }
    return false;
}

int main()
{
    Node *head = nullptr;
    insertAtEnd(head, 1);
    insertAtEnd(head, 2);
    insertAtEnd(head, 3);
    insertAtEnd(head, 4);
    insertAtEnd(head, 5);

    createLoop(head);

    detectLoop(head) ? cout << "Loop Detected.." << '\n' : cout << "No Loop Detected.." << '\n';
}

#include <iostream>
using namespace std;

struct hashing
{
    int value;
    int key;
};


void put(int value, hashing hash[],int n) {
    hash[value % n].value = value;
    hash[value % n].key = (value % n);
}

int get(int key, hashing hash[]) {
    return hash[key].value;
}

int main()
{
    int n;
    
    struct hashing hash[n];
    cin >> n;
    for (int t=0;t<n;t++) {
        put(t+1,hash,n);
        cout << "Inserted : " << (t+1) << endl;
    }
    int temp;
    cin >> temp;
    cout << get(temp,hash) << endl;
}

let url = URL(string: image.url)
let data = try? Data(contentsOf: url!) //make sure your image in this url does exist, otherwise unwrap in a if let check / try-catch
imageView.image = UIImage(data: data!)

//
//  GoogleSignInButtonView.swift
//
//  Created by Ivan Schaab on 11/09/2019.
//  Copyright © 2019 Ivan Schaab. All rights reserved.
//
import GoogleSignIn
import SwiftUI

struct GoogleSignInButtonView: View {

    @EnvironmentObject var lvm: LoginViewModel

    var body: some View {
        HStack {
            Spacer()
            GoogleButtonViewControllerRepresentable { (token, user) in
                // Google Login Success
                // Now do Backend Validations
                self.lvm.loginOauth(token: token, user: user)
            }
            Spacer()
        }.frame(alignment: .center)
    }
}

class GoogleButtonUIKitViewController: UIViewController {

    var signInButton = GIDSignInButton()

    override func viewDidLoad() {
        super.viewDidLoad()

        GIDSignIn.sharedInstance().clientID = Constants.GOOGLE_CLIENT_ID
        self.view.addSubview(signInButton)

        GIDSignIn.sharedInstance()?.presentingViewController = self

        // Automatically sign in the user.
        GIDSignIn.sharedInstance()?.restorePreviousSignIn()
    }
}

struct GoogleButtonViewControllerRepresentable: UIViewControllerRepresentable
{
    let vc = GoogleButtonUIKitViewController()
    var googleResponse: (String, User) -> Void

    func makeUIViewController(context: Context) -> GoogleButtonUIKitViewController {
        return vc
    }
    func updateUIViewController(_ uiViewController: GoogleButtonUIKitViewController, context: Context) {}
    func makeCoordinator() -> Coordinator {
        Coordinator(vc: vc, googleResponse: googleResponse)
    }

    static func dismantleUIViewController(_ uiViewController: GoogleButtonUIKitViewController, coordinator: GoogleButtonViewControllerRepresentable.Coordinator) {
        print("DISMANTLE")
    }

    class Coordinator: NSObject, GIDSignInDelegate  {
        var foo: (String, User) -> Void
        init(vc: GoogleButtonUIKitViewController, googleResponse: @escaping (String, User) -> Void) {
            self.foo = googleResponse
            super.init()
            GIDSignIn.sharedInstance()?.delegate = self
        }

        func sign(_ signIn: GIDSignIn!, didSignInFor googleUser: GIDGoogleUser!, withError error: Error!) {
            if let error = error {
                if (error as NSError).code == GIDSignInErrorCode.hasNoAuthInKeychain.rawValue {
                    print("The user has not signed in before or they have since signed out.")
                } else {
                    print("\(error.localizedDescription)")
                }
                return
            }
//            let userId = googleUser.userID                  // For client-side use only!
            let idToken = googleUser.authentication.idToken // Safe to send to the server
            let email = googleUser.profile.email

            if googleUser.profile.hasImage{
                let imageUrl = googleUser.profile.imageURL(withDimension: 120)
                print(" image url: ", imageUrl?.absoluteString ?? "NO URL")
            }

            let user : User = User(id: 1, name: googleUser.profile.givenName, surname: googleUser.profile.familyName, imgName: ""  , email: googleUser.profile.email)

            print("email: ",email ?? "NO EMAIL")

            foo(idToken! , user)
        }
    }
}



#if DEBUG
struct SomeRepView_Previews: PreviewProvider {
    static var previews: some View {
        GoogleSignInButtonView().environmentObject(LoginViewModel())
    }
}
#endif

private func deviceTokenDataToString(_ deviceToken: Data) -> String {
        let tokenChars = (deviceToken as NSData).bytes.assumingMemoryBound(to: CChar.self)
        var tokenString = ""

        for i in 0..<deviceToken.count {
            tokenString += String(format: "%02.2hhx", arguments: [tokenChars[i]])
        }

        return tokenString
    }

   func updateDeviceToken() {
        guard let deviceToken: Data = dataStorageService.value(for: .pushDeviceToken),
            deviceToken.isEmpty == false else {
                return
        }
        let stringPushToken = deviceTokenDataToString(deviceToken)
        mixpanel?.track(event: "Push Token Updated", properties: ["token": stringPushToken])
        peopleObject?.people.set(properties: ["$ios_devices": [stringPushToken]]
        mixpanel?.flush()
    }

struct ToggleView: View {
    @State private var toggleValue: Bool = true
    
    var body: some View {
        Toggle(isOn: $toggleValue, label: {})
            .toggleStyle(SwitchToggleStyle(tint: Color(red: 1.0, green: 0.5696961, blue: 0.9999913)))
            .introspectSwitch(customize: { (toggle) in
                toggle.thumbTintColor = UIColor.purple
            })
            .background(Color(red: 0.9529412, green: 0.9529412, blue: 0.18431373))
            .frame(width: DynamicSizeHelper.getWidth(322), height: DynamicSizeHelper.getHeight(31), alignment: .topLeading)
            .aspectRatio(contentMode: .fill)
            .labelsHidden()
    }
}

extension View {
    
    /// Hide or show the view based on a boolean value.
    ///
    /// Example for visibility:
    ///
    ///     Text("Label")
    ///         .isHidden(true)
    ///
    /// Example for complete removal:
    ///
    ///     Text("Label")
    ///         .isHidden(true, remove: true)
    ///
    /// - Parameters:
    ///   - hidden: Set to `false` to show the view. Set to `true` to hide the view.
    ///   - remove: Boolean value indicating whether or not to remove the view.
    @ViewBuilder func isHidden(_ hidden: Bool, remove: Bool = false) -> some View {
        if hidden {
            if !remove {
                self.hidden()
            }
        } else {
            self
        }
    }
}