Swift中extension的使用

由于swift中不可以使用宏定义，UI给的颜色标值，有的喜欢使用RGB有的直接 f5f5f5,所以声明两个UIcolor的extension方法

RGB

public static func RGB(R:Float,G:Float,B:Float,Alp:Float) -> UIColor {
        print(CGFloat(R/255))
        return UIColor.init(red: CGFloat(R/255.0), green: CGFloat(G/255.0), blue: CGFloat(B/255.0), alpha: CGFloat(Alp));
    }

HexStr

 public static func colorWithString(colorStr:NSString) -> UIColor{
        var cString = colorStr.trimmingCharacters(in: CharacterSet.ReferenceType.whitespacesAndNewlines) as String
        if (cString.count < 6) {
            return UIColor.clear
        }
        if cString.hasPrefix("0X") {
            cString  = String(cString[cString.index(cString.startIndex, offsetBy: 2)...])
        }
        if cString.hasPrefix("#") {
            cString  = String(cString[cString.index(cString.startIndex, offsetBy: 1)...])
        }
        
        if (cString.count != 6) {
            return UIColor.clear
        }
        let rstr = cString.mySubstring(start: 0, length: 2)
        let gstr = cString.mySubstring(start: 2, length: 2)
        let bstr = cString.mySubstring(start: 4, length: 2)
        
        var R = CUnsignedInt(),G = CUnsignedInt(),B = CUnsignedInt()
        Scanner.init(string: rstr).scanHexInt32(&R)
        Scanner.init(string: gstr).scanHexInt32(&G)
        Scanner.init(string: bstr).scanHexInt32(&B)
        return UIColor.init(red: CGFloat(R)/255.0, green: CGFloat(G)/255.0, blue: CGFloat(B)/255.0, alpha: CGFloat(1));
    }

swift里边字符串截取，个人感觉没有OC里边使用的方便

在下标为6 的字符开始截取，（包含下标为6的字符）效果与OC中substringFromIndex相同

        let hellor = "Hello,World"
        /*
         hellor.index("起始位置", offsetBy: "在起始位置偏移")
         */
        let myIndex = hellor.index(hellor.startIndex, offsetBy: 6)
        let subStr = String(hellor[myIndex..<hellor.endIndex])
        print(subStr)
        /*
         打印结果
         World
         */

在下标为0开始截取到下标为5的字符(..<不包括下标为5字符 ...包括下标为5字符)效果与OC中substringToIndex相同

        let myIndex = hellor.index(hellor.startIndex, offsetBy: 5)
        var subStr = String(hellor[..<myIndex])
        print(subStr)
        /*
         打印结果
            Hello
         */
        subStr = String(hellor[...myIndex])
        print(subStr)
        /*
         打印结果
            Hello,
         */

在指定位置向后截取指定长度的字符(包含指定位置的字符)效果与OC中的substringWithRange相同

        let startIndex = hellor.index(hellor.startIndex, offsetBy: 6)
        let len = hellor.index(startIndex, offsetBy: 3)
        let subStr = String(hellor[startIndex..<len])
        print(subStr)
        /*  打印结果
            Wor
         */

获取第一个满足指定字符之前的所有字符string.index(of: Character)

    let subStr = String(hellor[..<(hellor.index(of: ",") ?? hellor.endIndex)])
        print(subStr)
        /*
         Hello
         */

获取第一个满足指定字符之后的所有字符

 //向后偏移一个单位
        let stIndex = hellor.index((hellor.index(of: ",") ?? hellor.endIndex), offsetBy: 1)
        
        let subStr = String(hellor[stIndex..<hellor.endIndex])
        print(subStr)
        /*
         World
         */

个人感觉没有OC的简便。可以封装下使用，使用extension实现下

func mySubstring(to index:NSInteger) -> String {
        return String(self[..<self.index(self.startIndex, offsetBy: index)])
    }

        let hellor = "Hello,World"
        hellor.mySubstring(from: 3)
        hellor.mySubstring(to: 3)
        hellor.mySubstring(after: ",")
        hellor.mySubstring(before: ",")
        hellor.mySubstring(start: 2, length: 3)

其他功能的extension

• 判断是否是准确手机号、邮箱、身份证号、连接

func isMobileNumber() -> Bool{}
func isEmailAddress() -> Bool {}
func simpleVerifyIdentityCardNum() -> Bool {}
func isValidUrl() -> Bool {}

• 有时在开发中会遇到图片放大的展示功能，比如评论下的图片

//图片放大
    func showImage() -> Void {
        let image = self.image
        let window = UIApplication.shared.keyWindow
        let backgroundView = UIView.init(frame: CGRect.init(x: 0, y: 0, width: (window?.frame.size.width)!, height: (window?.frame.size.height)!))
        
        backgroundView.backgroundColor = UIColor.init(white: 0.441, alpha: 1.00)
        backgroundView.alpha = 0.0
        
        
        let imageView = UIImageView.init(frame: self.convert(self.bounds, to: window))
        imageView.image = image
        imageView.contentMode = UIViewContentMode.scaleAspectFit
        imageView.tag = 1
        backgroundView.addSubview(imageView)
        window?.addSubview(backgroundView)
        
        let tap = UITapGestureRecognizer.init(target: self, action: #selector(self.hideImage(tap:)))
        backgroundView.addGestureRecognizer(tap)
        
        UIView.animate(withDuration: 0.3, animations: {
            imageView.center = backgroundView.center
            backgroundView.alpha = 1
        }) { (finished) in
        }
    }

swift中不能声明宏定义，可以创建一个Const.swift文件
常量使用let声明，带有参数的使用方法实现，可以用类方法，在方法名前添加class或者static二选一

static func IsYESStrEmpty(obj:NSString?) -> Bool{}
class func IsNotStrEmpty( obj:NSString?) -> Bool{}

示例代码