设计模式05-SOLID(D)依赖倒置原则

Dependence Inversion Principle 依赖倒置原则

• Dependency Inversion：依赖倒置。即面向抽象/接口编程。可参考依赖倒置原则。面向抽象编程，可大大提高灵活度，因为抽象可继承实现，而所有实现均可替代抽象。

• 设计模式05-依赖倒置（依赖高层抽象，不应该依赖细节）
• 以下例子是人物关系：人-关系-人 的读取。  以下例子中我们不应该在Program构造中直接读取底层细节，而是通过高层抽象依赖去完成操作（接口间的依赖，你只需要这个接口能干什么就行，怎么实现的你别管，大可不必在逻辑中对底层对象进行冗余操作）

• enum RelationShip
              {
                  Parent,
                  Child,
                  Silbing
              }
              class Person
              {
                  public string Name;
                  public DateTime DateOfBirth;
              }
              interface ISearchRelationShip
              {
                  IEnumerable<Person> SearchChild(string parentName); 
              }
  
              class RelationShips: ISearchRelationShip
              {
                  private List<(Person, RelationShip, Person)> ps = new List<(Person, RelationShip, Person)>();
                  public void AddRelationShip(Person parent, Person child) 
                  {
                      ps.Add((parent, RelationShip.Parent, child));
                      ps.Add((child, RelationShip.Child, parent)); 
                  }
  
                  public IEnumerable<Person> SearchChild(string parentName)
                  {
                      foreach (var item in ps)
                      {
                          if (item.Item1.Name==parentName&&item.Item2==RelationShip.Parent)
                          {
                              yield return item.Item3;
                          }
                      }
                  }
              }
  
              internal class Program
              {
                  public Program(ISearchRelationShip searchRelationShip)
                  {
                      Console.WriteLine("zhangsan has childs:");
                      foreach (var item in searchRelationShip.SearchChild("zhangsan"))
                      {
                          Console.WriteLine($"    -{item.Name}");
                      } 
                  }
                  static void Main(string[] args)
                  {
                      Person father = new Person() { Name="zhangsan"};
                      Person child1 = new Person() { Name = "zhangdada" };
                      Person child2 = new Person() { Name = "zhangxiaoxiao" };
                      RelationShips rs = new RelationShips();
                      rs.AddRelationShip(father, child1);
                      rs.AddRelationShip(father, child2);
                      new Program(rs);
  
                  }
              }