Swift扩展示例

Question 1

我原本想知道如何做这样的事情

UIColor.myCustomGreen

这样我就可以定义自己的颜色并在整个应用程序中使用它们。

我之前研究过扩展，我认为我可以使用它们来解决问题，但是我不记得确切地如何设置扩展。在撰写本文时，在Google上搜索“ Swift扩展程序”导致了文档，一些冗长的教程以及一个相当无益的Stack Overflow问题。

因此答案是存在的，但是需要对文档和教程进行一些挖掘。我决定写这个问题和以下答案，以便为Stack Overflow添加一些更好的搜索关键字，并提供有关扩展程序设置方式的快速入门。

我特别想知道：

扩展驻留在哪里（文件和命名约定）？
扩展语法是什么？
有哪些简单的常用示例？

Question 2

创建扩展

使用File> New> File ...> iOS> Source> Swift File添加新的swift文件。您可以随心所欲地对其进行命名。

一般的命名约定是将其称为TypeName + NewFunctionality.swift。

范例1- `Double`

Double + Conversions.swift

import Swift // or Foundation

extension Double {

    func celsiusToFahrenheit() -> Double {
        return self * 9 / 5 + 32
    }

    func fahrenheitToCelsius() -> Double {
        return (self - 32) * 5 / 9
    }
}

用法：

let boilingPointCelsius = 100.0
let boilingPointFarenheit = boilingPointCelsius.celsiusToFahrenheit()
print(boilingPointFarenheit) // 212.0

示例2- `String`

字符串+快捷方式。swift

import Swift // or Foundation

extension String {

    func replace(target: String, withString: String) -> String {
        return self.replacingOccurrences(of: target, with: withString)
    }
}

用法：

let newString = "the old bike".replace(target: "old", withString: "new")
print(newString) // "the new bike"

这是一些更常见的String扩展。

范例3- `UIColor`

UIColor + CustomColor.swift

import UIKit

extension UIColor {

    class var customGreen: UIColor {
        let darkGreen = 0x008110
        return UIColor.rgb(fromHex: darkGreen)
    }

    class func rgb(fromHex: Int) -> UIColor {

        let red =   CGFloat((fromHex & 0xFF0000) >> 16) / 0xFF
        let green = CGFloat((fromHex & 0x00FF00) >> 8) / 0xFF
        let blue =  CGFloat(fromHex & 0x0000FF) / 0xFF
        let alpha = CGFloat(1.0)

        return UIColor(red: red, green: green, blue: blue, alpha: alpha)
    }
}

另请参阅此处。

用法：

view.backgroundColor = UIColor.customGreen

笔记

定义扩展后，它可以像内置类函数一样在应用程序中的任何位置使用。
如果不确定函数或属性的语法是什么样，可以Option+单击类似的内置方法。例如，当我Option+单击时，UIColor.greenColor我看到的声明是class func greenColor() -> UIColor。这为如何设置自定义方法提供了很好的线索。
Apple扩展文档
在Objective-C中，扩展称为类别。

Question 3

试试这个新的扩展方法：

UIColor

extension UIColor{
 //get new color from rgb value
  class func RGB(_ red:CGFloat , andGreenColor green:CGFloat, andBlueColor blue:CGFloat, withAlpha alpha:CGFloat) -> UIColor
  {
    let color = UIColor(red: red/255.0, green: green/255.0, blue: blue/255.0, alpha: alpha)
    return color
  }
}

 //return color from comma separated string of RGB paramater
  convenience init(rgbString :String, alpha:CGFloat = 1.0){
    let arrColor = rgbString.components(separatedBy: ",")
    let red:CGFloat = CGFloat(NumberFormatter().number(from: arrColor[0])!)
    let green:CGFloat = CGFloat(NumberFormatter().number(from: arrColor[1])!)
    let blue:CGFloat = CGFloat(NumberFormatter().number(from: arrColor[2])!)
    self.init(red: red/255.0, green: green/255.0, blue: blue/255.0, alpha: alpha)
  }

  //return color from hexadecimal value
  //let color2 = UIColor(rgbHexaValue: 0xFFFFFFFF)
  convenience init(rgbHexaValue: Int, alpha: CGFloat = 1.0) {
    self.init(red:  CGFloat((rgbHexaValue >> 16) & 0xFF), green: CGFloat((rgbHexaValue >> 8) & 0xFF), blue: CGFloat(rgbHexaValue & 0xFF), alpha: alpha)
  }
}

UITextField

extension UITextField{

//set cornerRadius
  func cornerRadius(){
    self.layoutIfNeeded()
    self.layer.cornerRadius = self.frame.height / 2
    self.clipsToBounds = true
  }

  //set bordercolor
  func borderColor(){
      self.layer.borderColor = TEXTFIELD_BORDER_COLOR.cgColor
      self.layer.borderWidth = 1.0
  }

  //set borderWidth
  func borderWidth(size:CGFloat){
    self.layer.borderWidth = size
  }

  //check textfield is blank
  func blank() -> Bool{
    let strTrimmed = self.text!.trim()//get trimmed string
    if(strTrimmed.characters.count == 0)//check textfield is nil or not ,if nil then return false
    {
      return true
    }
    return false
  }

  //set begginning space - left space
  func setLeftPadding(paddingValue:CGFloat) {
    let paddingView = UIView(frame: CGRect(x: 0, y: 0, width: paddingValue, height: self.frame.size.height))
    self.leftViewMode = .always
    self.leftView = paddingView
  }

  //set end of space
  func setRightPadding(paddingValue:CGFloat){
    let paddingView = UIView(frame: CGRect(x: (self.frame.size.width - paddingValue), y: 0, width: paddingValue, height: self.frame.size.height))
    self.rightViewMode = .always
    self.rightView = paddingView
  }
}

UIFont

extension UIFont{
 // Returns a scaled version of UIFont
  func scaled(scaleFactor: CGFloat) -> UIFont {
    let newDescriptor = fontDescriptor.withSize(fontDescriptor.pointSize * scaleFactor)
    return UIFont(descriptor: newDescriptor, size: 0)
  }
}

UIImage

public enum ImageFormat {
  case PNG
  case JPEG(CGFloat)
}


extension UIImage {
  //convert image to base64 string
  func toBase64() -> String {
    var imageData: NSData
    switch format {
    case .PNG: imageData = UIImagePNGRepresentation(self)! as NSData
    case .JPEG(let compression): imageData = UIImageJPEGRepresentation(self, compression)! as NSData
    }
    return imageData.base64EncodedString(options: .lineLength64Characters)
  }

  //convert string to image
  class func base64ToImage(toImage strEncodeData: String) -> UIImage {
    let dataDecoded  = NSData(base64Encoded: strEncodeData, options: NSData.Base64DecodingOptions.ignoreUnknownCharacters)!
    let image = UIImage(data: dataDecoded as Data)
    return image!
  }

  //Function for store file/Image into local directory. If image is already on the directory then first remove it and replace new image/File on that location
  func storedFileIntoLocal(strImageName:String) -> String{
    var strPath = ""
    let documentDirectory1 = NSString.init(string: String.documentDirectory())
    let imageName:String = strImageName + ".png"
    let imagePath = documentDirectory1.appendingPathComponent(imageName)
    strPath = imagePath
    let fileManager = FileManager.default
    let isExist = fileManager.fileExists(atPath: String.init(imagePath))
    if(isExist == true)
    {
      do {
        try fileManager.removeItem(atPath: imagePath as String)//removing file if exist
        // print("Remove success")
      } catch {
        print(error)
      }
    }
    let imageData:Data = UIImageJPEGRepresentation(self, 0.5)!
    do {
      try imageData.write(to: URL(fileURLWithPath: imagePath as String), options: .atomic)
    } catch {
      print(error)
      strPath = "Failed to cache image data to disk"
      return strPath
    }

    return strPath
  }


  //function for resize image
  func resizeImage(targetSize: CGSize) -> UIImage {
    let size = self.size

    let widthRatio  = targetSize.width  / self.size.width
    let heightRatio = targetSize.height / self.size.height

    // Figure out what our orientation is, and use that to form the rectangle
    var newSize: CGSize
    if(widthRatio > heightRatio) {
      newSize = CGSize(width: size.width * heightRatio, height: size.height * heightRatio)
    } else {
      //                        newSize = size
      newSize = CGSize(width: size.width * widthRatio,  height: size.height * widthRatio)
    }

    // This is the rect that we've calculated out and this is what is actually used below
    let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)

    // Actually do the resizing to the rect using the ImageContext stuff
    UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0)
    self.draw(in: rect)
    let newImage = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImage!
  }
}

日期

let YYYY_MM_DD_HH_MM_SS_zzzz = "yyyy-MM-dd HH:mm:ss +zzzz"
let YYYY_MM_DD_HH_MM_SS = "yyyy-MM-dd HH:mm:ss"
let DD_MM_YYYY = "dd-MM-yyyy"
let MM_DD_YYYY = "MM-dd-yyyy"
let YYYY_DD_MM = "yyyy-dd-MM"
let YYYY_MM_DD_T_HH_MM_SS = "yyyy-MM-dd'T'HH:mm:ss"

extension Date{

  //convert string to date
  static func convertStringToDate(strDate:String, dateFormate strFormate:String) -> Date{
    let dateFormate = DateFormatter()
    dateFormate.dateFormat = strFormate
    dateFormate.timeZone = TimeZone.init(abbreviation: "UTC")
    let dateResult:Date = dateFormate.date(from: strDate)!

    return dateResult
  }

  //Function for old date format to new format from UTC to local
  static func convertDateUTCToLocal(strDate:String, oldFormate strOldFormate:String, newFormate strNewFormate:String) -> String{
    let dateFormatterUTC:DateFormatter = DateFormatter()
    dateFormatterUTC.timeZone = NSTimeZone(abbreviation: "UTC") as TimeZone!//set UTC timeZone
    dateFormatterUTC.dateFormat = strOldFormate //set old Format
    if let oldDate:Date = dateFormatterUTC.date(from: strDate)  as Date?//convert date from input string
    {
      dateFormatterUTC.timeZone = NSTimeZone.local//set localtimeZone
      dateFormatterUTC.dateFormat = strNewFormate //make new dateformatter for output format
      if let strNewDate:String = dateFormatterUTC.string(from: oldDate as Date) as String?//convert dateInUTC into string and set into output
      {
        return strNewDate
      }
      return strDate
    }
    return strDate
  }

  //Convert without UTC to local
  static func convertDateToLocal(strDate:String, oldFormate strOldFormate:String, newFormate strNewFormate:String) -> String{
    let dateFormatterUTC:DateFormatter = DateFormatter()
    //set local timeZone
    dateFormatterUTC.dateFormat = strOldFormate //set old Format
    if let oldDate:Date = dateFormatterUTC.date(from: strDate) as Date?//convert date from input string
    {
      dateFormatterUTC.timeZone = NSTimeZone.local
      dateFormatterUTC.dateFormat = strNewFormate //make new dateformatter for output format
      if let strNewDate = dateFormatterUTC.string(from: oldDate as Date) as String?//convert dateInUTC into string and set into output
      {
        return strNewDate
      }
      return strDate
    }
    return strDate
  }

  //Convert Date to String
  func convertDateToString(strDateFormate:String) -> String{
      let dateFormatter = DateFormatter()
      dateFormatter.dateFormat = strDateFormate
      let strDate = dateFormatter.string(from: self)
//      dateFormatter = nil
      return strDate
  }


  //Convert local to utc
  static func convertLocalToUTC(strDate:String, oldFormate strOldFormate:String, newFormate strNewFormate:String) -> String{
    let dateFormatterUTC:DateFormatter = DateFormatter()
    dateFormatterUTC.timeZone = NSTimeZone.local as TimeZone!//set UTC timeZone
    dateFormatterUTC.dateFormat = strOldFormate //set old Format
    if let oldDate:Date = dateFormatterUTC.date(from: strDate)  as Date?//convert date from input string
    {
      dateFormatterUTC.timeZone = NSTimeZone.init(abbreviation: "UTC")! as TimeZone//set localtimeZone
      dateFormatterUTC.dateFormat = strNewFormate //make new dateformatter for output format
      if let strNewDate:String = dateFormatterUTC.string(from: oldDate as Date) as String?//convert dateInUTC into string and set into output
      {
        return strNewDate
      }
      return strDate
    }
    return strDate
  }

  //Comparison two date
  static func compare(date:Date, compareDate:Date) -> String{
    var strDateMessage:String = ""
    let result:ComparisonResult = date.compare(compareDate)
    switch result {
    case .orderedAscending:
      strDateMessage = "Future Date"
      break
    case .orderedDescending:
      strDateMessage = "Past Date"
      break
    case .orderedSame:
      strDateMessage = "Same Date"
      break
    default:
      strDateMessage = "Error Date"
      break
    }
    return strDateMessage
  }
}

调用此函数：

let color1 = UIColor.RGB(100.0, andGreenColor: 200.0, andBlueColor: 300.0, withAlpha: 1.0)
let color2 = UIColor.init(rgbHexaValue: 800000, alpha: 1.0)
let color3 = UIColor.init(rgbString: ("100.0,200.0,300.0", alpha: 1.0)

self.txtOutlet.cornerRadius()
self.txtOutlet.borderColor()
self.txtOutlet.setLeftPadding(paddingValue: 20.0)
self.txtOutlet.setRightPadding(paddingValue: 20.0)

let yourScaledFont = self.dependentView.font.scaled(scaleFactor: n as! CGFloat)
let base64String = (image?.toBase64(format: ImageFormat.PNG))!
let resultImage = UIImage.base64ToImage(toImage: base64String)
let path = yourImage.storedFileIntoLocal(strImageName: "imagename")

Question 4

Swift 3.0示例：

extension UITextField 
{    

    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
    }
}

Question 5

在文字下划线 `UITextField`

用于功能 ViewDidLoad()

firstNametext.underlined(0.5)

延期

extension UITextField {

    func underlined(_ size:Double){
        let border = CALayer()
        let width = CGFloat(size)
        border.borderColor = UIColor.red.cgColor
        border.frame = CGRect(x: 0, y: self.frame.size.height - width, 
        width:  self.frame.size.width, height: self.frame.size.height)
        border.borderWidth = width
        self.layer.addSublayer(border)
        self.layer.masksToBounds = true }
    }
}

Question 6

UIColor + util.swift

import UIKit


extension UIColor{


    class func getCustomBlueColor() -> UIColor
    {
        return UIColor(red:0.043, green:0.576 ,blue:0.588 , alpha:1.00)
    }

    func getNameofColour() ->String
    {
        return "myOrange"
    }

}

用法：

NSLog("\(UIColor.getCustomBlueColor())")
let color=UIColor(red:0.043, green:0.576 ,blue:0.588 , alpha:1.00);
NSLog(color.getNameofColour())

希望您看到有什么不同。以类func开头的Function之一，仅以func开头的Function之一。您可以使用自己喜欢的东西。

Question 7

扩展和便捷初始化程序的最佳示例之一：

 extension UIActivityIndicatorView {
    convenience init(activityIndicatorStyle: UIActivityIndicatorViewStyle, color: UIColor, placeInTheCenterOf parentView: UIView) {
    self.init(activityIndicatorStyle: activityIndicatorStyle)
    center = parentView.center
    self.color = color
    parentView.addSubview(self)
  }
}

您可以通过以下方式使用它：

初始化活动指示器

let activityIndicator = UIActivityIndicatorView(activityIndicatorStyle: .whiteLarge, color: .gray,  placeInTheCenterOf: view)

开始制作动画活动指示器
```
activityIndicator.startAnimating()
```
停止动画活动指示器
```
activityIndicator.stopAnimating()
```

Question 8

如果您喜欢使用具有给定色彩的颜色，如品牌手册中所使用的： Swift 4.2 + xcode 9.4.1。

extension UIColor {
    func withTint(tint: CGFloat)->UIColor {

        var tint = max(tint, 0)
        tint = min(tint, 1)
        /* Collect values of sender */
        var r : CGFloat = 0
        var g : CGFloat = 0
        var b : CGFloat = 0
        var a : CGFloat = 0
        self.getRed(&r, green: &g, blue: &b, alpha: &a)

        /* Calculate the tint */
        r = r+(1-r)*(1-tint)
        g = g+(1-g)*(1-tint)
        b = b+(1-b)*(1-tint)
        a = 1

        return UIColor.init(red: r, green: g, blue: b, alpha: a)
    }
}

在你的代码中

let redWithTint = UIColor.red.withTint(tint: 0.4)

Question 9

这是一个引人注目的动画效果的扩展示例，该效果可与UITableView中的单元格一起使用。滚动UITableView时，每个单元格都从点源增长到正常大小。根据需要调整动画时间。

由于每个单元格在滚动时会出现一点点时间错位，因此效果会很好地波动！请观看展示效果的15秒剪辑：https : //www.youtube.com/watch?v=BVeQpno56wU&feature=youtu.be


extension UITableViewCell {

    func growCellDuringPresentation(thisCell : UITableViewCell) {

        thisCell.transform = CGAffineTransform(scaleX: 0.01, y: 0.01)

        UIView.animate(withDuration: TimeInterval(0.35), delay: 0.0, options: UIView.AnimationOptions.allowUserInteraction,   animations: {

            thisCell.transform = CGAffineTransform(scaleX: 1, y: 1)

        }, completion: nil)

    }
}

要使用扩展名，您需要在cellForRowAt返回单元格之前对其进行调用，如下所示：


            cell.growCellDuringPresentation(thisCell: cell)
            return cell

请注意，当为集合视图返回单元格时，此方法也适用。

这是一个功能完全相同的扩展，除了它在演示过程中旋转单元格外：


extension UITableViewCell {

    func rotateCellDuringPresentation(thisCell : UITableViewCell) {

        thisCell.transform = CGAffineTransform(rotationAngle: .pi)

        UIView.animate(withDuration: TimeInterval(0.35), delay: 0.0, options: UIView.AnimationOptions.allowUserInteraction,   animations: {

            thisCell.transform = CGAffineTransform(rotationAngle: 0)

        }, completion: nil)

    }
}

它被类似地称为：


            cell.rotateCellDuringPresentation(thisCell: cell)
            return cell

这是沿相同线的延伸，沿X方向平移单元


extension UITableViewCell {

    func translateCellDuringPresentation(thisCell : UITableViewCell) {

        thisCell.layer.transform = CATransform3DMakeTranslation(-300, 0, 0)

        UIView.animate(withDuration: TimeInterval(0.5), delay: 0.0, options: UIView.AnimationOptions.allowUserInteraction,   animations: {

            thisCell.layer.transform = CATransform3DMakeTranslation(0, 0, 0)

        }, completion: nil)

    }
}

它被类似地称为：


            cell.translateCellDuringPresentation(thisCell: cell)
            return cell

Swift扩展示例

创建扩展

范例1- Double

示例2- String

范例3- UIColor

笔记

UIColor

UITextField

UIFont

UIImage

日期

在文字下划线 UITextField

范例1- `Double`

示例2- `String`

范例3- `UIColor`

在文字下划线 `UITextField`