24个好用的Extension让代码更整洁

24个好用的Extension让代码更整洁(转自Medium)

扩展(Extension)是swift和oc最好用的功能之一，能够无侵入的对现有系统类和工程添加新方法

作为一个iOS和Android的双料开发者，我经常能看到Android代码的功能方法更简洁，易懂；

当然通过扩展，我们也可以把这些特性使用在swift上，使swift项目也更精炼，更加好用

以下代码是基于swift，但其实对于oc，大部分也可以很容易的移植

1.String.trim() and Swift.trimmed

我们经常会用到string的trim功能，帮助把string里的空格，制表符，换行符等特殊符号去掉

扩展可以这么写

import Foundation

extension String {
    var trimmed: String {
        self.trimmingCharacters(in: .whitespacesAndNewlines)
    }
    
    mutating func trim() {
        self = self.trimmed
    }
}

用法：

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var str1 = "  a b c d e   \n"
var str2 = str1.trimmed
str1.trim()

2. Int.toDouble() and Double.toInt()

Int和Double,CGFloat的转换是项目中经常会用到.但实际使用上遇到Double(a),必须要求a是非可选类型,所以经常要做额外处理

可以对Int和Double的扩展:

import Foundation

extension Int {
    func toDouble() -> Double {
        Double(self)
    }
}

extension Double {
    func toInt() -> Int {
        Int(self)
    }
}

用法:

1 2	let a = 15.78 let b = a.toInt()

3. String.toDate(…) and Date.toString(…)

对Date和String的转换做易用的封装

扩展:

import Foundation

extension String {
    func toDate(format: String) -> Date? {
        let df = DateFormatter()
        df.dateFormat = format
        return df.date(from: self)
    }
}

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

用法:

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let strDate = "2020-08-10 15:00:00"
let date = strDate.toDate(format: "yyyy-MM-dd HH:mm:ss")
let strDate2 = date?.toString(format: "yyyy-MM-dd HH:mm:ss")

4.Int.fenToYuan()

没什么可说的,金额的分转元

扩展:


import Foundation

extension Int {
    func fenToYuan() -> Double {
        Double(self) / 100
    }
}

用法:

1 2	let fen = 12350 let yuan = fen.fenToYuan()

5.String.asCoordinates()

string转成坐标,包括两个值,精度和纬度,在3D场景下还有高度数据,高度不是很常用

我们根据string里的逗号来解析,转成CLLocationCoordinate2D对象

扩展

import Foundation
import CoreLocation

extension String {
    var asCoordinates: CLLocationCoordinate2D? {
        let components = self.components(separatedBy: ",")
        if components.count != 2 { return nil }
        let strLat = components[0].trimmed
        let strLng = components[1].trimmed
        if let dLat = Double(strLat),
            let dLng = Double(strLng) {
            return CLLocationCoordinate2D(latitude: dLat, longitude: dLng)
        }
        return nil
    }
}

用法:

1 2	let strCoordinates = "41.6168, 41.6367" let coordinates = strCoordinates.asCoordinates

6.String.asURL()

URL是用处理链接的常用类,很灵活,可以连接不同组建,可以把各种类型处理为URLs,同时,也经常会配合着string的使用

扩展:

import Foundation

extension String {
    var asURL: URL? {
        URL(string: self)
    }
}

用法:

1 2	let strUrl = "https://medium.com" let url = strUrl.asURL

7.UIDevice.vibrate()

iPhone的震动效果是手机行业内做的最好的,可以主动调用这个

扩展:

import UIKit
import AudioToolbox

extension UIDevice {
    static func vibrate() {
        AudioServicesPlaySystemSound(1519)
    }
}

用法:

1	UIDevice.vibrate()

8.String.width(…) and String.height(…)

计算UILabel里的text占用的宽度,根据Font计算

扩展:

import UIKit

extension String {
    func height(withConstrainedWidth width: CGFloat, font: UIFont) -> CGFloat {
        let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)
        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [.font: font], context: nil)

        return ceil(boundingBox.height)
    }

    func width(withConstrainedHeight height: CGFloat, font: UIFont) -> CGFloat {
        let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)
        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [.font: font], context: nil)

        return ceil(boundingBox.width)
    }
}

extension NSAttributedString {
    func height(withConstrainedWidth width: CGFloat) -> CGFloat {
        let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)
        let boundingBox = boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, context: nil)

        return ceil(boundingBox.height)
    }

    func width(withConstrainedHeight height: CGFloat) -> CGFloat {
        let constraintRect = CGSize(width: .greatestFiniteMagnitude, height: height)
        let boundingBox = boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, context: nil)

        return ceil(boundingBox.width)
    }
}

用法:

1 2	let text = "Hello, world!" let textHeight = text.height(withConstrainedWidth: 100, font: UIFont.systemFont(ofSize: 16))

9.String.containsOnlyDigits

检查string是否只含有数字

扩展:

import Foundation

extension String {
    var containsOnlyDigits: Bool {
        let notDigits = NSCharacterSet.decimalDigits.inverted
        return rangeOfCharacter(from: notDigits, options: String.CompareOptions.literal, range: nil) == nil
    }
}

用法:

1 2	let digitsOnlyYes = "1234567890".containsOnlyDigits let digitsOnlyNo = "12345+789".containsOnlyDigits

10.String.isAlphanumeric

检查string是否只有数字和大小写字母,经常用于密码格式验证

扩展

import Foundation

extension String {
    var isAlphanumeric: Bool {
        !isEmpty && range(of: "[^a-zA-Z0-9]", options: .regularExpression) == nil
    }
}

用法:

1 2	let alphanumericYes = "asd3kJh43saf".isAlphanumeric let alphanumericNo = "Kkncs+_s3mM.".isAlphanumeric

11.String 下标

swift的截取内容是比较繁琐的,比如:获取第n位内容,可以只设置一个Int参数

扩展:

import Foundation

extension String {
    subscript (i: Int) -> Character {
        return self[index(startIndex, offsetBy: i)]
    }
    
    subscript (bounds: CountableRange<Int>) -> Substring {
        let start = index(startIndex, offsetBy: bounds.lowerBound)
        let end = index(startIndex, offsetBy: bounds.upperBound)
        if end < start { return "" }
        return self[start..<end]
    }
    
    subscript (bounds: CountableClosedRange<Int>) -> Substring {
        let start = index(startIndex, offsetBy: bounds.lowerBound)
        let end = index(startIndex, offsetBy: bounds.upperBound)
        if end < start { return "" }
        return self[start...end]
    }
    
    subscript (bounds: CountablePartialRangeFrom<Int>) -> Substring {
        let start = index(startIndex, offsetBy: bounds.lowerBound)
        let end = index(endIndex, offsetBy: -1)
        if end < start { return "" }
        return self[start...end]
    }
    
    subscript (bounds: PartialRangeThrough<Int>) -> Substring {
        let end = index(startIndex, offsetBy: bounds.upperBound)
        if end < startIndex { return "" }
        return self[startIndex...end]
    }
    
    subscript (bounds: PartialRangeUpTo<Int>) -> Substring {
        let end = index(startIndex, offsetBy: bounds.upperBound)
        if end < startIndex { return "" }
        return self[startIndex..<end]
    }
}

用法:

1 2	let subscript1 = "Hello, world!"[7...] let subscript2 = "Hello, world!"[7...11]

12. UIImage.squared

如果需要用户提交一张方形照片,他们很少有标准的方形照片,但一般App里的头像控件往往都是圆形或者方形的

这个扩展可以快速的做处理

扩展:

import UIKit

extension UIImage {
    var squared: UIImage? {
        let originalWidth  = size.width
        let originalHeight = size.height
        var x: CGFloat = 0.0
        var y: CGFloat = 0.0
        var edge: CGFloat = 0.0
        
        if (originalWidth > originalHeight) {
            // landscape
            edge = originalHeight
            x = (originalWidth - edge) / 2.0
            y = 0.0
            
        } else if (originalHeight > originalWidth) {
            // portrait
            edge = originalWidth
            x = 0.0
            y = (originalHeight - originalWidth) / 2.0
        } else {
            // square
            edge = originalWidth
        }
        
        let cropSquare = CGRect(x: x, y: y, width: edge, height: edge)
        guard let imageRef = cgImage?.cropping(to: cropSquare) else { return nil }
        
        return UIImage(cgImage: imageRef, scale: scale, orientation: imageOrientation)
    }
}

以上是类方法,也可以改为成实例方法

用法:

1 2	let img = UIImage() // Must be a real UIImage let imgSquared = img.squared // img.squared() for method

13.UIImage.resized(…)

图片资源上传服务器的时候,会有大小限制,往往会处理成一张小尺寸照片

扩展:

import UIKit

extension UIImage {
    func resized(maxSize: CGFloat) -> UIImage? {
        let scale: CGFloat
        if size.width > size.height {
            scale = maxSize / size.width
        }
        else {
            scale = maxSize / size.height
        }
        
        let newWidth = size.width * scale
        let newHeight = size.height * scale
        UIGraphicsBeginImageContext(CGSize(width: newWidth, height: newHeight))
        draw(in: CGRect(x: 0, y: 0, width: newWidth, height: newHeight))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return newImage
    }
}

用法

1 2	let img2 = UIImage() // Must be a real UIImage let img2Thumb = img2.resized(maxSize: 512)

可以结合第12条一起使用

1 2	let img = UIImage() // Must be a real UIImage let imgPrepared = img.squared?.resized(maxSize: 512)

14.Int.toString()

一般可以用”‘\(num)”的方法把Int类型转为string,但是有个问题,如果你的num是可选类型,则会把”optional”也加进去,Kotlin处理可选类型比较优雅:对任意类型someVar?.toString,返回可选string

可惜,swift不允许对Any扩展,但至少可以给Int加上

扩展

import Foundation

extension Int {
    func toString() -> String {
        "\(self)"
    }
}

用法

1 2	let i1 = 15 let i1AsString = i1.toString()

15.Double.toString()

和14同理,对Double加toString方法,但限制是保留两位小数

扩展:

import Foundation

extension Double {
    func toString() -> String {
        String(format: "%.02f", self)
    }
}

用法:

1 2	let d1 = 15.67 let d1AsString = d1.toString()

16.Double.toPrice()

用的地方不多,转成”323,232,21.33$”这种格式

扩展:

import Foundation

extension Double {
    func toPrice(currency: String) -> String {
        let nf = NumberFormatter()
        nf.decimalSeparator = ","
        nf.groupingSeparator = "."
        nf.groupingSize = 3
        nf.usesGroupingSeparator = true
        nf.minimumFractionDigits = 2
        nf.maximumFractionDigits = 2
        return (nf.string(from: NSNumber(value: self)) ?? "?") + currency
    }
}

用法:

1 2	let dPrice = 16.50 let strPrice = dPrice.toPrice(currency: "€")

17.String.asDict

把JSON格式的string拆成字典,swift很方便

扩展:


import Foundation

extension String {
    var asDict: [String: Any]? {
        guard let data = self.data(using: .utf8) else { return nil }
        return try? JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [String: Any]
    }
}

用法:

1 2	let json = "{\"hello\": \"world\"}" let dictFromJson = json.asDict

18.String.asArray

和上个类似,转成集合类型

扩展:

import Foundation

extension String {
    var asArray: [Any]? {
        guard let data = self.data(using: .utf8) else { return nil }
        return try? JSONSerialization.jsonObject(with: data, options: .allowFragments) as? [Any]
    }
}

用法:

1 2	let json2 = "[1, 2, 3]" let arrFromJson2 = json2.asArray

19.String.asAttributedString

有时我们需要一些跨平台的文本格式,最常用的是HTML格式,UILabel可以对粗体,下划线等要是做处理.把HTML格式转成NSAttributedString格式,然后给UILabel.attributedText赋值使用

扩展:

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import Foundation

extension String {
var asAttributedString: NSAttributedString? {
guard let data = self.data(using: .utf8) else { return nil }
return try? NSAttributedString(data: data, options: [.documentType: NSAttributedString.DocumentType.html], documentAttributes: nil)
}
}

用法:

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let htmlString = "<p>Hello, <strong>world!</string></p>"
let attrString = htmlString.asAttributedString

20.Bundle.appVersion
可以从Info.plist里加载app的版本信息,用途有:

获取版本信息

检查是否有更新

展示版本信息

支持邮件里包含版本信息

扩展:

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import Foundation

extension Bundle {
var appVersion: String? {
self.infoDictionary?["CFBundleShortVersionString"] as? String
}

static var mainAppVersion: String? {
Bundle.main.appVersion
}
}

用法:

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let appVersion = Bundle.mainAppVersion

原文:

https://medium.com/better-programming/24-swift-extensions-for-cleaner-code-41e250c9c4c3

原文确实只有20个…

24个好用的Extension让代码更整洁