Step 1:

let alertVC = UIAlertController(title: "Enter credentials", message: "Provide Email & Password", preferredStyle: .alert)

Step 2:

alertVC.addTextField { (textField) in
    textField.placeholder = "Email"
}
alertVC.addTextField { (textField) in
    textField.placeholder = "Password"
    textField.isSecureTextEntry = true
}

Step 3:

let submitAction = UIAlertAction(title: "Submit", style: .default, handler: {
    (alert) -> Void in
    
    let emailTextField = alertVC.textFields![0] as UITextField
    let passwordTextField = alertVC.textFields![1] as UITextField
    
    print("Email -- \(emailTextField.text!), Password -- \(passwordTextField.text!)")
})

Step 4:

alertVC.addAction(submitAction)
alertVC.view.tintColor = UIColor.black
present(alertVC, animated: true)

1. +(_:_:) generic operator:

var arr1 = [1, 2, 3]
let arr2 = [4, 5, 6]
let finalArray = arr1 + arr2
print(finalArray)
// output will be '[1, 2, 3, 4, 5, 6]'

2. append(contentsOf:):

var arr1 = [1, 2, 3]
let arr2 = [4, 5, 6]
arr1.append(contentsOf: arr2)
print(arr1)
// output will be '[1, 2, 3, 4, 5, 6]'

3. flatMap(_:):

var arr1 = [1, 2, 3]
let arr2 = [4, 5, 6]
let finalArray = [arr1, arr2].flatMap({ (element: [Int]) -> [Int] in
    return element
})
print(finalArray)
// output will be '[1, 2, 3, 4, 5, 6]'

4. joined():

var arr1 = [1, 2, 3]
let arr2 = [4, 5, 6]
let flattenCollection = [arr1, arr2].joined()
let finalArray = Array(flattenCollection)
print(finalArray)
// output will be '[1, 2, 3, 4, 5, 6]'

5. reduce(_:_:):

var arr1 = [1, 2, 3]
let arr2 = [4, 5, 6]
let finalArray = [arr1, arr2].reduce([], { (result: [Int], element: [Int]) -> [Int] in
    return result + element
})
print(finalArray)
// output will be '[1, 2, 3, 4, 5, 6]'

let friends = ["Sophia", "James", "Olivia", "Mike", "Nina"]
print(friends.sorted())

//output is '["James", "Mike", "Nina", "Olivia", "Sophia"]'

struct friendStruct {
    var name: String
    var age: Int
}

let array = [
    friendStruct(name: "Sophia", age: 23),
    friendStruct(name: "Olivia", age: 25),
    friendStruct(name: "James", age: 21),
    friendStruct(name: "Nina", age: 26),
    friendStruct(name: "Mike", age: 23)
]

Sort by name:

let sortedArray = array.sorted { (firstStruct, secondStruct) -> Bool in
    if firstStruct.name < secondStruct.name {
        return true
    }
    return false
}

Sort by age:

let sortedArray = array.sorted { (firstStruct, secondStruct) -> Bool in
    if firstStruct.age < secondStruct.age {
        return true
    }
    return false
}

Date Formats:

One Date Format To Another:

extension String
{
    func toDateString( inputDateFormat inputFormat  : String,  ouputDateFormat outputFormat  : String ) -> String
    {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = inputFormat
        let date = dateFormatter.date(from: self)
        dateFormatter.dateFormat = outputFormat
        return dateFormatter.string(from: date!)
    }
}

Usage:

let dateString = "2017-10-10 15:56:25"
let requiredFormat = dateString.toDateString(inputDateFormat: "yyyy-MM-dd HH:mm:ss", ouputDateFormat: "dd 'at' hh:mm:ss")
print(requiredFormat)

//output will be '10 at 03:56:25'

Date To String:

extension Date
{
    func toString( dateFormat format  : String ) -> String
    {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = format
        return dateFormatter.string(from: self)
    }
}

Usage:

let dateString = Date().toString(dateFormat: "yyyy/MMM/dd HH:mm:ss")
print("dateString is \(dateString)")

// output will be 'dateString is 2017/Oct/11 17:16:23'

String To Date:

extension String
{
    func toDate( dateFormat format  : String) -> Date
    {
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = format
        dateFormatter.timeZone = NSTimeZone(name: "UTC") as TimeZone!
        return dateFormatter.date(from: self)!
    }
    
}

Usage:

let dateString = "2017-10-10 15:56:25"
let date = dateString.toDate(dateFormat: "yyyy-MM-dd HH:mm:ss")
print("Date is \(date)")

// output is 'Date is 2017-10-10 15:56:25 +0000'

UTC to Local:

func UTCToLocal(UTCDateString: String) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss" //Input Format
    dateFormatter.timeZone = NSTimeZone(name: "UTC") as TimeZone!
    let UTCDate = dateFormatter.date(from: UTCDateString)
    dateFormatter.dateFormat = "yyyy-MMM-dd hh:mm:ss" // Output Format
    dateFormatter.timeZone = TimeZone.current
    let UTCToCurrentFormat = dateFormatter.string(from: UTCDate!)
    return UTCToCurrentFormat
}

Usage:

let dateString = "2017-10-10 9:56:25"

let date = self.UTCToLocal(UTCDateString: dateString)

//output date should be '2017-10-10 15:26:25'

Local to UTC:

func localToUTC(date:String) -> String {
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss"
    dateFormatter.calendar = NSCalendar.current
    dateFormatter.timeZone = TimeZone.current
    
    let dt = dateFormatter.date(from: date)
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    dateFormatter.dateFormat = "yyyy-MMM-dd hh:mm:ss"
    
    return dateFormatter.string(from: dt!)
}

Usage:

let dateString = "2017-10-10 15:56:25"

let date = self.localToUTC(date: dateString)

//output date should be '2017-10-10 09:26:25'

pod 'Firebase/Storage'

Configure Firebase Storage Rules:

// Anyone can read or write to the bucket, even non-users of your app.
// Because it is shared with Google App Engine, this will also make
// files uploaded via GAE public.
service firebase.storage {
  match /b/{bucket}/o {
    match /{allPaths=**} {
      allow read, write;
    }
  }
}

Set up Firebase Storage To iOS Project :

import Firebase

// Use Firebase library to configure APIs
FirebaseApp.configure()

let storage = Storage.storage()

Create a Reference To upload, download, or delete:

// Create a storage reference from our storage service
let storageRef = storage.reference()

var carRef = storageRef.child("images/car.jpg")

Uploading To Cloud Storage :

func uploadImageToStorage() {
    let storage = Storage.storage()
    var storageRef = storage.reference()
    
    if let image = UIImage(named: "car.jpg") {
        let data = UIImagePNGRepresentation(image)
        print("data \(String(describing: data))")
        
        
        // Create the file metadata
        let metadata = StorageMetadata()
        metadata.contentType = "image/jpeg"
        
        storageRef = storageRef.child("images/car.jpg")
        
        let uploadTask = storageRef.putData(data!, metadata: metadata)
        
        // Listen for state changes, errors, and completion of the upload.
        uploadTask.observe(.resume) { snapshot in
            // Upload resumed, also fires when the upload starts
        }
        
        uploadTask.observe(.pause) { snapshot in
            // Upload paused
        }
        
        uploadTask.observe(.progress) { snapshot in
            // Upload reported progress
            let percentComplete = 100.0 * Double(snapshot.progress!.completedUnitCount)
                / Double(snapshot.progress!.totalUnitCount)
            
            print("Upload Percentage == \(percentComplete)")
        }
        
        uploadTask.observe(.success) { snapshot in
            // Upload completed successfully
            print("Upload completed successfully")
        }
        
        uploadTask.observe(.failure) { snapshot in
            if let error = snapshot.error as? NSError {
                switch (StorageErrorCode(rawValue: error.code)!) {
                case .objectNotFound:
                    // File doesn't exist
                    break
                case .unauthorized:
                    // User doesn't have permission to access file
                    break
                case .cancelled:
                    // User canceled the upload
                    break
                    
                    /* ... */
                    
                case .unknown:
                    // Unknown error occurred, inspect the server response
                    break
                default:
                    // A separate error occurred. This is a good place to retry the upload.
                    break
                }
            }
        }
    }
}

Downloading Image From Cloud Storage:

func downloadImageFromStorage() {
    let storage = Storage.storage()
    var storageRef = storage.reference()
    
    // Create a reference to the file we want to download
    storageRef = storageRef.child("images/car.jpg")
    
    // Start the download (in this case writing to a file)
    let downloadTask = storageRef.getData(maxSize: 5 * 1024 * 1024) { data, error in
        if let error = error {
            // Uh-oh, an error occurred!
        } else {
            // Data for "images/island.jpg" is returned
            let image = UIImage(data: data!)
            
            print("image succesfully downloaded \(image!)")
        }
    }
    
    
    // Observe changes in status
    downloadTask.observe(.resume) { snapshot in
        // Download resumed, also fires when the download starts
    }
    
    downloadTask.observe(.pause) { snapshot in
        // Download paused
    }
    
    downloadTask.observe(.progress) { snapshot in
        // Download reported progress
        let percentComplete = 100.0 * Double(snapshot.progress!.completedUnitCount)
            / Double(snapshot.progress!.totalUnitCount)
    }
    
    downloadTask.observe(.success) { snapshot in
        // Download completed successfully
    }
    
    // Errors only occur in the "Failure" case
    downloadTask.observe(.failure) { snapshot in
        guard let errorCode = (snapshot.error as? NSError)?.code else {
            return
        }
        guard let error = StorageErrorCode(rawValue: errorCode) else {
            return
        }
        switch (error) {
        case .objectNotFound:
            // File doesn't exist
            break
        case .unauthorized:
            // User doesn't have permission to access file
            break
        case .cancelled:
            // User cancelled the download
            break
            
            /* ... */
            
        case .unknown:
            // Unknown error occurred, inspect the server response
            break
        default:
            // Another error occurred. This is a good place to retry the download.
            break
        }
    }
}

Deleting Image From Firebase Storage:

func deletingImageFromStorage(){
    let storage = Storage.storage()
    var storageRef = storage.reference()
    
    // Create a reference to the file we want to download
    storageRef = storageRef.child("images/car.jpg")
    
    storageRef.delete { error in
        if let error = error {
            // Uh-oh, an error occurred!
        } else {
            print("File deleted successfully")
        }
    }
    
}

• Bottom layout guide & top layout guide are deprecated from iOS 11.

• We can change safeArea layout insets by using a safeAreaInsets property.

• safeAreaInsetsDidChange() method will call when the safe area of the view changes.

Safe area layout guide Using Storyboards:

Safe area layout guide Programmatically:

Code:

Conclusion:

• The safeAreaLayoutGuide is a property of UIView where topLayoutGuide and bottomLayoutGuide are properties of UIViewController

• The constraintEqualToSystemSpacingBelow method is new in iOS 11 and removes the need to hard code standard spacing. There are also less than and greater than versions. For horizontal spacing there is also constraintEqualToSystemSpacingAfter.

• We can increase or decrease of safe area size using safeAreaInsets property.

Next Steps :

iOS 11[Swift 4] Navigation Bar With Large Titles and LargeTitleTextAttributes

Data Structure:

Getting Started:

Set up Firebase Cloud Firestore To iOS Project :

pod 'Firebase/Core'
pod 'Firebase/Firestore'

import Firebase

// Use Firebase library to configure APIs
FirebaseApp.configure()

Saving/Adding data to Cloud Firestore:

var docRef : DocumentReference!

docRef = Firestore.firestore().document("friends/profile")

@IBAction func saveButtonTapped(_ sender: UIButton) {
    guard let name = nameField.text, !name.isEmpty else { return }
    guard let profession = professionField.text, !profession.isEmpty else { return }
    
    let dataToSave : [String: Any] = ["name": name, "profession": profession]
    docRef.setData(dataToSave) { (error) in
        if let error = error {
            print("Oh no! Some error \(error.localizedDescription)")
        }else {
            print("Data has been saved")
        }
    }
}

Fetching/Getting data From Cloud Firestore:

@IBAction func fetchButtonTapped(_ sender: Any) {
    docRef.getDocument { (docSnapshot, error) in
        guard let docSnapshot = docSnapshot, docSnapshot.exists else { return }
        let data = docSnapshot.data()
        let name = data["name"] as? String ?? ""
        let profession = data["profession"] as? String ?? ""
        self.titleLabel.text = "\(name) is a \(profession)"
    }
}

Listening for RealTime in Cloud Firestore:

var dataListener : FIRListenerRegistration!

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    dataListener =  docRef.addSnapshotListener { (docSnapshot, error) in
        guard let docSnapshot = docSnapshot, docSnapshot.exists else { return }
        let data = docSnapshot.data()
        let name = data["name"] as? String ?? ""
        let profession = data["profession"] as? String ?? ""
        self.titleLabel.text = "\(name) is a \(profession)"
    }
}

override func viewWillDisappear(_ animated: Bool) {
    super.viewWillDisappear(animated)
    dataListener.remove()
}

Conclusion:

pod 'Firebase/Database'

Configure Firebase Database Rules:

Authenticate with Firebase using Facebook Login

Firebase Authentication using Email & Password

Authenticate with Firebase Anonymously on iOS

// These rules give anyone, even people who are not users of your app,
// read and write access to your database
{
  "rules": {
    ".read": true,
    ".write": true
  }
}

Set up Firebase Realtime Database :

import Firebase

// Use Firebase library to configure APIs
FirebaseApp.configure()

var ref: DatabaseReference!

ref = Database.database().reference()

Writing Data:

•     NSString

•     NSNumber

•     NSDictionary

•     NSArray

ref.child("users").setValue(["username": "Jhon"])

Reading Data By Listening :

func readData() {
    let userRef = Database.database().reference().child("users")
    let refHandle : DatabaseHandle!
    refHandle = userRef.observe(.value, with: { (snapshot) in
        let userDict = snapshot.value as? [String : AnyObject] ?? [:]
        print(userDict)
        // ...
    })
}

if let handle = refHandle {
    Database.database().reference().removeObserver(withHandle: handle)
}

SingleEvent Observer:

let userID = Auth.auth().currentUser?.uid
ref.child("users").observeSingleEvent(of: .value, with: { (snapshot) in
  // Get user value
  let value = snapshot.value as? NSDictionary
  let username = value?["username"] as? String ?? ""
  let user = User.init(username: username)

  // ...
  }) { (error) in
    print(error.localizedDescription)
}