String+Extensions.swift

import Foundation

extension String {
    
    // MARK: 计算字符串的 MD5 哈希值
    var md5: String? {
        let length = Int(CC_MD5_DIGEST_LENGTH)
        
        guard let data = self.data(using: String.Encoding.utf8) else { return nil }
        
        let hash = data.withUnsafeBytes { (bytes: UnsafeRawBufferPointer) -> [UInt8] in
            var hash: [UInt8] = [UInt8](repeating: 0, count: Int(CC_MD5_DIGEST_LENGTH))
            CC_MD5(bytes.baseAddress, CC_LONG(data.count), &hash)
            return hash
        }
        
        return (0..<length).map { String(format: "%02x", hash[$0]) }.joined()
    }
    
    // MARK: 返回本地化字符串
    var localized: String {
        NSLocalizedString(self, comment: "")
    }
    
    // MARK: 字符串截取
    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]
    }
    
    // MARK: 内容校验
    var containsOnlyDigits: Bool {
        let notDigits = NSCharacterSet.decimalDigits.inverted
        return rangeOfCharacter(from: notDigits, options: String.CompareOptions.literal, range: nil) == nil
    }
    
    var containsOnlyLetters: Bool {
        let notLetters = NSCharacterSet.letters.inverted
        return rangeOfCharacter(from: notLetters, options: String.CompareOptions.literal, range: nil) == nil
    }
    
    var isAlphanumeric: Bool {
        let notAlphanumeric = NSCharacterSet.decimalDigits.union(NSCharacterSet.letters).inverted
        return rangeOfCharacter(from: notAlphanumeric, options: String.CompareOptions.literal, range: nil) == nil
    }
    
    // MARK: 校验电子邮件地址有效性
    // 用法：let approved = "test@test.com".isValidEmail // true
    var isValidEmail: Bool {
        let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,64}"

        let emailTest = NSPredicate(format: "SELF MATCHES %@", emailRegEx)
        return emailTest.evaluate(with: self)
    }
    
    // MARK: String 类型转换为 Int 类型
    func toInt() -> Int {
        Int(self)!
    }
    
    func toIntOrNull() -> Int? {
        Int(self)
    }
    
    /**
     将字符分组
     
     用法：
     var cardNumber = "1234567890123456"
     cardNumber.insert(separator: " ", every: 4)
     print(cardNumber)
     // 1234 5678 9012 3456
     
     let pin = "7690"
     let pinWithDashes = pin.inserting(separator: "-", every: 1)
     print(pinWithDashes)
     // 7-6-9-0
     */
    mutating func insert(separator: String, every n: Int) {
        self = inserting(separator: separator, every: n)
    }
    
    func inserting(separator: String, every n: Int) -> String {
        var result: String = ""
        let characters = Array(self)
        stride(from: 0, to: count, by: n).forEach {
            result += String(characters[$0..<min($0+n, count)])
            if $0+n < count {
                result += separator
            }
        }
        return result
    }
}