Important Extension Used in Swift for adding more functionality in iOS App.

Extension.swift

// Extension Used for showing Country,City from lat long 

extension UIViewController{

    func fetchCountryAndCity(location: CLLocation, completion: @escaping (String, String) -> ()) {
        CLGeocoder().reverseGeocodeLocation(location) { placemarks, error in
            if let error = error {
                print(error)
            } else if let country = placemarks?.first?.country,
                let city = placemarks?.first?.locality {
                completion(country, city)
            }
        }
    }
}

Usage :- 
        let location = CLLocation(latitude: latitude, longitude: longitude)

        fetchCountryAndCity(location: location) { country, city in
            print("country:", country)
            print("city:", city)
            
            self.txtField.text = "\(city),\(country)"
        }

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// Underline of UILabel

extension UILabel{
    
    func underlineLabel() {
        if let textString = self.text {
            let attributedString = NSMutableAttributedString(string: textString)
            attributedString.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.styleSingle.rawValue, range: NSRange(location: 0, length: attributedString.length - 1))
            attributedText = attributedString
        }
    }
}

Usage:- 
      self.lblDealDescription.underlineLabel()
 ***************************************************************************************************************************

extension UIView{
    func setBottomBorder() {
        self.layer.masksToBounds = false
        self.layer.shadowColor = UIColor.gray.cgColor
        self.layer.shadowOffset = CGSize(width: 0.0, height: 1.0)
        self.layer.shadowOpacity = 1.0
        self.layer.shadowRadius = 0.0
    }
    
    func setRoundEdge() {
        self.layer.borderWidth = 1.0
        self.layer.cornerRadius = 5.0
        self.layer.borderColor = UIColor.lightGray.cgColor
        self.layer.masksToBounds = true
        self.clipsToBounds = true
    }
    
    func viewBorder() {
        self.layer.cornerRadius = 3.0
        self.layer.borderWidth = 1.0
        self.layer.borderColor = UIColor.lightGray.cgColor
        self.layer.masksToBounds = true
    }
}
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// Entension of Image for resizing of image before uploading to server 

extension UIImage {
    
  // First Method
    var highestQualityJPEGNSData: NSData { return UIImageJPEGRepresentation(self, 1.0)! as NSData }
    var highQualityJPEGNSData: NSData    { return UIImageJPEGRepresentation(self, 0.75)! as NSData}
    var mediumQualityJPEGNSData: NSData  { return UIImageJPEGRepresentation(self, 0.5)! as NSData }
    var lowQualityJPEGNSData: NSData     { return UIImageJPEGRepresentation(self, 0.25)! as NSData}
    var lowestQualityJPEGNSData: NSData  { return UIImageJPEGRepresentation(self, 0.0)! as NSData }
 
  // Second Method 
    func resized(withPercentage percentage: CGFloat) -> UIImage? {
        let canvasSize = CGSize(width: size.width * percentage, height: size.height * percentage)
        UIGraphicsBeginImageContextWithOptions(canvasSize, false, scale)
        defer { UIGraphicsEndImageContext() }
        draw(in: CGRect(origin: .zero, size: canvasSize))
        return UIGraphicsGetImageFromCurrentImageContext()
    }
    
    // Third Method
    func resizedTo1MB() -> UIImage? {
        guard let imageData = UIImagePNGRepresentation(self) else { return nil }
        
        var resizingImage = self
        var imageSizeKB = Double(imageData.count) / 1000.0 // ! Or devide for 1024 if you need KB but not kB
        
        while imageSizeKB > 1000 { // ! Or use 1024 if you need KB but not kB
            guard let resizedImage = resizingImage.resized(withPercentage: 0.9),
                let imageData = UIImagePNGRepresentation(resizedImage)
                else { return nil }
            
            resizingImage = resizedImage
            imageSizeKB = Double(imageData.count) / 1000.0 // ! Or devide for 1024 if you need KB but not kB
        }
        
        return resizingImage
    }
    
}
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// Date Extension 
public extension Date {
    
    public func dateString (format: String = "dd MMM, yyyy") -> String {
        let formatter = DateFormatter()
        formatter.dateFormat = format
        return formatter.string(from: self)
    } 
}
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// TextField Extension 

extension UITextField
{
    enum Direction
    {
        case Right
        case Left
    }
    func AddImage(direction:Direction,imageName:String,Frame:CGRect)
    {
        let View = UIView(frame: Frame)
        let imageView = UIImageView(frame: Frame)
        imageView.image = UIImage(named: imageName)
        View.addSubview(imageView)
        if Direction.Right == direction
        {
            self.rightViewMode = .always
            self.rightView = View
        }
        else{
            self.leftViewMode = .always
            self.leftView = View
        }
    }
    
    func setLeftPaddingPoints(_ amount:CGFloat){
        let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: amount, height: self.frame.size.height))
        self.leftView = paddingView
        self.leftViewMode = .always
    }
    func setRightPaddingPoints(_ amount:CGFloat) {
        let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: amount, height: self.frame.size.height))
        self.rightView = paddingView
        self.rightViewMode = .always
    }
    
    func textfieldBorder() {
        self.layer.cornerRadius = 3.0
        self.layer.borderWidth = 1.0
        self.layer.borderColor = UIColor.lightGray.cgColor
        self.layer.masksToBounds = true
    }
    
    func placeholderColor(_ color: UIColor){
            var placeholderText = ""
            if self.placeholder != nil{
                placeholderText = self.placeholder!
            }
        self.attributedPlaceholder = NSAttributedString(string: placeholderText,
                                                        attributes: [NSForegroundColorAttributeName: UIColor.lightGray])
    }
    
}



   func AddLeftImage(_ imageNamed: String){
        let imageView = UIImageView(frame: CGRect(x: 0, y: 1, width: self.frame.height,height: self.frame.height-2 ))
        imageView.image = UIImage(named: imageNamed)
        imageView.contentMode = UIViewContentMode.scaleAspectFit     
        self .setValue(UIColor.lightGray, forKeyPath: "_placeholderLabel.textColor")
        self.leftView  = imageView
        self.leftViewMode = UITextFieldViewMode.always
        self.addSubview(imageView)
    }

    func AddRightImage(_ imageNamed: String){
        let imageView = UIImageView(frame: CGRect(x: 0, y: 1, width: self.frame.height,height: self.frame.height-2 ))
        imageView.image = UIImage(named: imageNamed)
        imageView.contentMode = UIViewContentMode.scaleAspectFit
        self .setValue(UIColor.lightGray, forKeyPath: "_placeholderLabel.textColor")
        self.rightView  = imageView
        self.rightViewMode = UITextFieldViewMode.always
        self.addSubview(imageView)
    }
    
    func changePlaceholderColor(color : UIColor){
       self .setValue(color, forKeyPath: "_placeholderLabel.textColor")
    }

    func useTopUnderline() {
        let border = CALayer()
        let borderWidth = CGFloat(1.0)
        border.borderColor = UIColor.lightGray.cgColor
        border.frame = CGRect(origin: CGPoint(x: 0,y :0), size: CGSize(width: self.frame.size.width, height: 1))
        border.borderWidth = borderWidth
        self.layer.addSublayer(border)
        self.layer.masksToBounds = true
    }
    
    
    func useUnderline() {
        let border = CALayer()
        let borderWidth = CGFloat(1.0)
        border.borderColor = UIColor.lightGray.cgColor
        border.frame = CGRect(origin: CGPoint(x: 0,y :self.frame.size.height - borderWidth), size: CGSize(width: self.frame.size.width, height: self.frame.size.height))
        border.borderWidth = borderWidth
        self.layer.addSublayer(border)
        self.layer.masksToBounds = true
    }
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// Extension of Alert Controller 
extension UIViewController {
    func alertMessageShow(title: String, message: String) {
        let alert = UIAlertController(title: title, message: message, preferredStyle: UIAlertControllerStyle.alert)
        let action = UIAlertAction(title: "OK", style: .default, handler: nil)
        alert.addAction(action)
        present(alert, animated: true, completion: nil)
    }
}
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// Checking Internet Connection

extension UIViewController{
    
    func isInternetAvailable() -> Bool
    {
        var zeroAddress = sockaddr_in()
        zeroAddress.sin_len = UInt8(MemoryLayout<sockaddr_in>.size)
        zeroAddress.sin_family = sa_family_t(AF_INET)
        
        guard let defaultRouteReachability = withUnsafePointer(to: &zeroAddress, {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) {
                SCNetworkReachabilityCreateWithAddress(nil, $0)
            }
        }) else {
            return false
        }
        var flags: SCNetworkReachabilityFlags = []
        if !SCNetworkReachabilityGetFlags(defaultRouteReachability, &flags) {
            return false
        }
        let isReachable = flags.contains(.reachable)
        let needsConnection = flags.contains(.connectionRequired)
        return (isReachable && !needsConnection)
    }
}

Usage:- 

import SystemConfiguration // import 

 override func viewDidLoad() {
        super.viewDidLoad()

        if (!self.isInternetAvailable()){
            // Internet connection not available 
            self.alertMessageShow(title: "No Internet Connection", message: "Make sure your device is connected to the internet.")
        }
        else{
            //Internet connection available
        }
    }