【愚公系列】2021年12月 二十三种设计模式(十六)-迭代器模式(Iterator Pattern)

namespace IteratorPattern

public class Person {
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public Person(string firstName, string lastName) {
        this.FirstName = firstName;
        this.LastName = lastName;
    }
}

public class People : IEnumerable {
    private Person[] _people = null;
    public People(Person[] pArray) {
        _people = new Person[pArray.Length];
        for (int i = 0; i < pArray.Length; i++) {
            _people[i] = pArray[i];
        }
    }
    public IEnumerator GetEnumerator() {
        return new PeopleEnum(_people);
    }
}

public class PeopleEnum : IEnumerator {
    private Person[] _people = null;
    private int _cursor = -1;
    public PeopleEnum(Person[] list) {
        _people = list;
    }
    public bool MoveNext() {
        _cursor++;
        return (_cursor < _people.Length);
    }
    public void Reset() {
        _cursor = -1;
    }
    public object Current {
        get {
            try {
                return _people[_cursor];
            }
            catch (IndexOutOfRangeException) {
                throw new InvalidOperationException();
            }
        }
    }
}

public class ApplePhone {
    public string PhoneName { get; set; }
    public DateTime PublishedDate { get; set; }
}

public class BestEnum {
    public static IEnumerable<ApplePhone> GetIPhones() {
        yield return new ApplePhone {
            PhoneName = "IPhone",
            PublishedDate = new DateTime(2007, 1, 9)
        };
        yield return new ApplePhone {
            PhoneName = "IPhone 3G",
            PublishedDate = new DateTime(2008, 6, 10)
        };
        yield return new ApplePhone {
            PhoneName = "IPhone 3GS",
            PublishedDate = new DateTime(2009, 6, 9)
        };
        yield return new ApplePhone {
            PhoneName = "IPhone 4",
            PublishedDate = new DateTime(2010, 6, 8)
        };
        //部分代码已省略
    }
}

public class Program {
    protected const string LINE_BREAK =
        "---------------------------------------------";
    public static void Main(string[] args) {
        var peopleArray = new Person[]
        {
            new Person("John", "Smith"),
            new Person("Jim", "Johnson"),
            new Person("Sue", "Rabon")
        };
        var peopleList = new People(peopleArray);
        foreach(Person p in peopleList)
            Console.WriteLine(p.FirstName + " " + p.LastName);
        Console.WriteLine(LINE_BREAK);
        var iterator = peopleList.GetEnumerator();
        while(iterator.MoveNext()) {
            var person = iterator.Current as Person;
            Console.WriteLine(person.FirstName + " " + person.LastName);
        }
        Console.WriteLine(LINE_BREAK);
        foreach(var phone in BestEnum.GetIPhones()) {
            Console.WriteLine("[" + phone.PhoneName + "] was released in " +
                              phone.PublishedDate.ToString("yyyy-MM-dd") + "!");
        }
        Console.WriteLine(LINE_BREAK);
        Console.ReadKey();
    }
}

John Smith
Jim Johnson
Sue Rabon
---------------------------------------------
John Smith
Jim Johnson
Sue Rabon
---------------------------------------------
[IPhone] was released in 2007-01-09!
[IPhone 3G] was released in 2008-06-10!
[IPhone 3GS] was released in 2009-06-09!
[IPhone 4] was released in 2010-06-08!
[IPhone 4s] was released in 2011-10-04!
[IPhone 5] was released in 2012-09-13!
[IPhone 5S] was released in 2013-09-10!
[IPhone 5C] was released in 2013-09-10!
[IPhone 6] was released in 2014-09-10!
[IPhone 6 Plus] was released in 2014-09-10!
[IPhone 6s] was released in 2015-09-10!
[IPhone 6s Plus] was released in 2015-09-10!
[IPhone 7] was released in 2016-09-08!
[IPhone 7 Plus] was released in 2016-09-08!
[IPhone 8] was released in 2017-09-13!
[IPhone 8 Plus] was released in 2017-09-13!
[IPhone X] was released in 2017-09-13!
---------------------------------------------