代理模式讲解

protocol ExamCandidate: class {
    
    func answerTheQuestion()
}

class LazyStudent: ExamCandidate {
    var name: String
    
    init(name: String) {
        self.name = name
    }
    
    func answerTheQuestion() {
    }
}

class Gunman: ExamCandidate {
    var name: String
    var target: LazyStudent?
    
    init(name: String) {
        self.name = name
    }
    
    func answerTheQuestion() {
        if let stu = target {
            print("姓名: \(stu.name)")
            print("奋笔疾书答案")
            print("提交试卷")
        }
    }
}

let stu = LazyStudent(name: "王大锤")
let gun = Gunman(name: "骆昊")
gun.target = stu
gun.answerTheQuestion()

委托回调模式讲解

protocol ExamDelegate: class {
    
    func answerTheQuestion()
}

class LazyStudent {
    var name: String
    weak var delegate: ExamDelegate?
    
    init(name: String) {
        self.name = name
    }
    
    func joinExam() {
        print("姓名: \(name)")
        delegate?.answerTheQuestion()
    }
}
class Gunman: ExamDelegate {
    
    func answerTheQuestion() {
        print("奋笔疾书各种答案")
    }
}

let stu = LazyStudent(name: "王大锤")
let gun = Gunman()
stu.delegate = gun
stu.joinExam()

字符串中各个数字或字母的获取

extension String {
    
    var length: UInt32 {
        get { return UInt32(self.characters.count) }
    }
    
    subscript(index: Int) -> Character {
        get { return self[self.startIndex.advancedBy(index)] }
    }
}

func randomInt(min: UInt32, _ max: UInt32) -> Int {
    return Int(arc4random_uniform(max - min + 1) + min)
}

func generateVerificationCode(length: Int) -> String {
    var code = ""
    if length > 0 {
        let str = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
        for _ in 0..<length {
            code.append(str[randomInt(0, str.length - 1)])
        }
    }
    return code
}

for _ in 1...10 {
    print(generateVerificationCode(4))
}