Question

在下面的例子中，据我所知，IComparable方法CompareTo被用作基本方法。我想在类中实现Interface方法（CompareTo）是不是必须的？下面的例子没有这样做。刚用过它。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace test
{
public class MyClass<T> where T : IComparable<T>
{
    public void GetBiggerValue(T Value1, T Value2)
    {
        if (Value1.CompareTo(Value2) > 0)
        {
            Console.WriteLine("{0} is bigger than {1}", Value1, Value2);
        }

        if (Value1.CompareTo(Value2) == 0)
        {
            Console.WriteLine("{0} is equal to {1}", Value1, Value2);
        }

        if (Value1.CompareTo(Value2) < 0)
        {
            Console.WriteLine("{0} is smaller than {1}", Value1, Value2);
        }
    }
}

class Program
{
    static void Main(string[] args)
    {
        Program p = new Program();

        MyClass<int> mcInt = new MyClass<int>();
        MyClass<string> mcString = new MyClass<string>();

        mcInt.GetBiggerValue(124, 126);             //126          

        Console.ReadKey();
    }
}
}

Answer 1

在

 public class MyClass<T> where T : IComparable<T>

MyClass类型未实现（或“继承”）IComparable<T>，但它要求其类型参数T执行。

在您的测试用例中，类型int和string是满足此约束的类型。

Answer 2

必须实施T MyClass<T>，而不是IComparable<T>：

 where T : IComparable<T> // <- It is T that's restricted

在你的情况下：

 // T == int; int is comparable (implements IComparable<int>)
 MyClass<int> mcInt = ...

 // T == string; string is comparable (implements IComparable<string>)
 MyClass<string> mcString = ...

如果您提出MyClass<int[]>（int[]未实施IComparable<int[]>），您将遇到编译时错误

修改：您当前的实施存在一些问题：

// Technically, you don't want any MyClass<T> instance
//TODO: change into static: public static void GetBiggerValue(T Value1, T Value2
public void GetBiggerValue(T Value1, T Value2) {
  //DONE: Value1 can well be null; Value1.CompareTo(...) will throw exception then
  //DONE: CompareTo can be expensive, compute it once
  int compare = (null == Value1) 
    ? (null == Value2 ? 0 : -1) // null equals to null, but less any other value
    : Value1.CompareTo(Value2);

  // A shorter alternative is 
  // int compare = Comparer<T>.Default.Compare(Value1, Value2);

  //DONE: if ... else if is more readable construction in the context 
  if (compare > 0) 
    Console.WriteLine("{0} is bigger than {1}", Value1, Value2);
  else if (compare < 0)
    Console.WriteLine("{0} is smaller than {1}", Value1, Value2);
  else  
    Console.WriteLine("{0} is equal to {1}", Value1, Value2);
}

IComparable <t>继承还是接口？

2 个答案: