Question

我现在正在Nutshell中阅读c＃6.0这本书，下面的代码是关于“实现IComparable接口”的主题。

我没有得到一些东西：

为什么IComparable.CompareTo在那里明确实施？
如果只是CompareTo的另一个隐式重载（一个隐含的重载）会怎样 int CompareTo (Note other)，另一个隐含int CompareTo (object other)？

public struct Note : IComparable<Note>, IEquatable<Note>, IComparable
{
   int _semitonesFromA;
   public int SemitonesFromA { get { return _semitonesFromA; } }

   public Note (int semitonesFromA)
   {
     _semitonesFromA = semitonesFromA;
   }

   public int CompareTo (Note other) // Generic IComparable<T>
   {
   if (Equals (other)) return 0; // Fail-safe check
   return _semitonesFromA.CompareTo (other._semitonesFromA);
   }

   int IComparable.CompareTo (object other) // Nongeneric IComparable
   {
   if (!(other is Note))
   throw new InvalidOperationException ("CompareTo: Not a note");
   return CompareTo ((Note) other);
   }

   public static bool operator < (Note n1, Note n2)
     => n1.CompareTo (n2) < 0;

   public static bool operator > (Note n1, Note n2)
     => n1.CompareTo (n2) > 0;

   public bool Equals (Note other) // for IEquatable<Note>
     => _semitonesFromA == other._semitonesFromA;

   public override bool Equals (object other)
   {
   if (!(other is Note)) return false;
   return Equals ((Note) other);
   }

   public override int GetHashCode() => _semitonesFromA.GetHashCode();
   public static bool operator == (Note n1, Note n2) => n1.Equals (n2);
   public static bool operator != (Note n1, Note n2) => !(n1 == n2);
}

Answer 1

你可以隐含地实施IComparable，是的。但从根本上说，您希望阻止用户将Note与其他Note以外的任何内容进行比较。如果IComparable，您可能会有遗留用法，但如果有任何关于Note课程的直接知道，您就不想允许：

Note note = new Note();
Other other = new Other();
int result = note.CompareTo(other);

你知道这总会引发异常，为什么要允许呢？基本上，将非通用IComparable接口视为＆＃34;有点遗留＆＃34; （有效用途，但......）并且不鼓励任何人明确地实施它。

实现IComparable接口

1 个答案: