实践观察者模式

    通过实现读者，出版社，报纸之间的关系，实践设计模式中的观察者模式。

1.Person类

 public class Person
    {
        public string Name { get; set; }
        public Newspaper  Newspaper { get; set; }
        public Person(string name)
        {
            this.Name = name;
        }
        public void SetNewspaper(Newspaper paper)
        {
            this.Newspaper = paper;
        }
    }

2.Newspaper类

public class Newspaper
    {
        public string Title { get; set; }
        public string Content { get; set; }

        public Newspaper(string title, string content)
        {
            this.Title = title;
            this.Content = content;
        }
    }

3.Publisher

  public class Publisher
    {
        public string Name { get; set; }
        public Publisher(string name)
        {
            this.Name = name;
        }

        public List<Person> Persons = new List<Person>();
        public void SendNewspaper(Newspaper paper)
        {
            Persons.ForEach(person=>person.SetNewspaper(paper));
        }
    }

4.main函数

class Program
    {
        static void Main(string[] args)
        {
            Publisher p = new Publisher("出版社");
            p.Persons.Add(new Person("April"));
            p.Persons.Add(new Person("harris"));
            p.SendNewspaper(new Newspaper ("人民日报","为人民服务"));
        }
    }

1.观察模式又叫订阅\发布模式。

2.Publisher类维护一个读者列表，发布Newspaper时，遍历这个列表，实施发布。

3.Publisher类不承担读者注册的责任，读者在类外部注册到读者列表中，使得Publisher类的代码耦合性较低。