Removing viewcontrollers from navigation stack

When session expired move to login page : Removing viewcontrollers from navigation stack

//If session expaired move to login page

if message == "Session Expired" {

    DispatchQueue.main.async {

        //Check navigation stacks

        let navigationArray = self.navigationController?.viewControllers //To get all UIViewController stack as Array

        print(navigationArray!)//Prints navigation stacks

        //Remove all navigations

        self.navigationController!.viewControllers.removeAll()

        //Remoce particular VC navigation

        //self.navigationController?.viewControllers.remove(at: "insert here a number")

        //Check navigation stacks

        let navigationArray2 = self.navigationController?.viewControllers //To get all UIViewController stack as Array

        print(navigationArray2 as Any)//Prints nill

        //Check whether the user logined or not

        UserDefaults.standard.set(false, forKey: "isUserLoggedIn")

        //Clear user defaults

        SharedClass.sharedInstance.clearDataFromUserDefaults()

        let lvc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "LVC") as! LoginViewController

        let appDelegate = UIApplication.shared.delegate as! AppDelegate

        appDelegate.window?.rootViewController = lvc                                

    }

}

What is UIWindow in iOS?

Window property :

var window: UIWindow?

the window property used to present the app’s visual content on the device’s main screen.

Normally, Xcode provides your app's main window. New iOS projects use storyboards to define the app’s views. Storyboards require the presence of a window property on the app delegate object, which the Xcode templates automatically provide. If your app does not use storyboards, you must create this window yourself.

Errors in iOS

Errors : 

1) Expression type '@lvalue CGRect' is ambiguous without more context

Code: 

Wrote this code in JSON response 

if status == "SUCCESS" {

    self.myTableView = UITableView(frame: CGRect(x: 0, y: 0, width: self.subView.frame.width, height: tblViewDescArray.count*50)) //Error comes here self.subView.frame.width

    self.subView.addSubview(self.myTableView)

} 

Solution :  https://stackoverflow.com/questions/51140220/swift-4-expression-type-value-cgrect-is-ambiguous-without-more-context

let width = self.subView.frame.width

                                

self.myTableView = UITableView(frame: CGRect(x: 0, y: 0, width: Int(width), height: self.tblViewDescArray.count*50))

2) Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

Solution : Here tableView IBOutlet not available in this VC.

Navigation types in iOS

Navigation in normal approach :

let cdplvc = self.storyboard?.instantiateViewController(withIdentifier: "CDPLVC") 

self.navigationController?.pushViewController(cdplvc!, animated: false)

In PageViewController : 

let cdplvc = self.storyboard?.instantiateViewController(withIdentifier: "CDPLVC") 

//We need to fix it navigation

(UIApplication.shared.keyWindow?.rootViewController as? UINavigationController)?.pushViewController(csvc!, animated: true)

Ex. PageViewController : https://stackoverflow.com/questions/56801714/in-pageviewcontroller-navigation-not-working

Set navigation bar back button :

 In pageViewController :

let csvc = self.storyboard?.instantiateViewController(withIdentifier: "CSVC")

let backButton = UIBarButtonItem()

//backItem.title = "Login"

backButton.barButtonTitle(titleString:"Status”)//Through extension class

(UIApplication.shared.keyWindow?.rootViewController as? UINavigationController)?.self.navigationBar.topItem?.backBarButtonItem = backButton

(UIApplication.shared.keyWindow?.rootViewController as? UINavigationController)?.pushViewController(csvc!, animated: true)

extension UIBarButtonItem {

    func barButtonTitle(titleString:String) { 

        title = titleString

        if UIDevice.current.userInterfaceIdiom == .pad {

            setTitleTextAttributes([NSAttributedString.Key.font: UIFont(name: "Medium", size: 20)!], for: UIControl.State.normal);

        } else {

            setTitleTextAttributes([NSAttributedString.Key.font: UIFont(name: "Medium", size: 15)!], for: UIControl.State.normal);

        }        

    }

}

In Normal approach :

let cdplvc = self.storyboard?.instantiateViewController(withIdentifier: "CDPLVC") 

        

let backItem = UIBarButtonItem()

backItem.title = "Login"

self.navigationItem.backBarButtonItem = backItem

//If required font size etc…

if UIDevice.current.userInterfaceIdiom == .pad {

     backItem.setTitleTextAttributes([NSAttributedString.Key.font: UIFont(name: "Medium", size: 20)!], for: UIControl.State.normal);

} else {

     backItem.setTitleTextAttributes([NSAttributedString.Key.font: UIFont(name: "Medium", size: 15)!], for: UIControl.State.normal);

}

        

self.navigationController?.pushViewController(cdplvc!, animated: false)

Make ViewController as Transparent view (Create Transparent view with ViewController)

//create view controller

let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "CEVC")

       

//remove black screen in background

vc.modalPresentationStyle = .overCurrentContext

//add clear color background

vc.view.backgroundColor = UIColor.black.withAlphaComponent(0.4)

            

//present modal

self.present(vc!, animated: false, completion: nil)

Convert Array, Dictionary into JSON in Swift :

Convert Dictionary into JSON in Swift :

From:  https://stackoverflow.com/questions/29625133/convert-dictionary-to-json-in-swift

let dic = ["2": "B", "1": "A", "3": "C"]

let encoder = JSONEncoder()

if let jsonData = try? encoder.encode(dic) {

    if let jsonString = String(data: jsonData, encoding: .utf8) {

        print(jsonString)

    }

}

Convert Array in to JSON in Swift

From :  https://riptutorial.com/ios/example/28692/convert-array-into-json-string

let array = [["prod_uniq" : "5cb5d3aecd4d9"], ["Quantity" : "500"], ["Amount" : "1000"]]

        

let jsonString = convertIntoJSONString(arrayObject: array)

print("jsonString - \(jsonString ?? "Empty JSON")")

        

func convertIntoJSONString(arrayObject: [Any]) -> String? {

        

        do {

            let jsonData: Data = try JSONSerialization.data(withJSONObject: arrayObject, options: [])

            if  let jsonString = NSString(data: jsonData, encoding: String.Encoding.utf8.rawValue) {

                return jsonString as String

            }

            

        } catch let error as NSError {

            print("Array convertIntoJSON - \(error.description)")

        }

        return nil

    }

Call function in iOS

//Eable call function

    @IBAction func onClickCallBtn(_ sender: Any) {

        guard let url = URL(string: "tel://self.mobile") else {

            return //be safe

        }

        

        if #available(iOS 10.0, *) {

            UIApplication.shared.open(url)

        } else {

            UIApplication.shared.openURL(url)

        }

    }