C# - ジェネリックとコレクション(IComparer<T>)

開発環境

• Microsoft Windows 7 Home Premium (OS)
• Microsoft Visual C# 2010 Express Edition (IDE)
• 言語: C#

『初めてのC# 第2版』(Jesse Liberty+Brian MacDonald著、日向俊二訳、オライリー・ジャパン、2006年、ISBN978-487311-294-7)の 第14章(ジェネリックとコレクション)14.6(練習問題)、練習14-4を解いてみる。

練習14-4.

コード

using System;
using System.Collections.Generic;

namespace Sample
{
    abstract class Animal : IComparable<Animal>
    {
        private int weight;
        private string name;
        public Animal(int weight, string name)
        {
            this.weight = weight;
            this.name = name;
        }
        public abstract void Speak();
        public abstract void Move();
        public override string ToString()
        {
            return "Name: " + name +
                " Weight: " + weight;
        }
        #region IComparable
        public int CompareTo(Animal rhs)
        {
            return this.weight.CompareTo(rhs.weight);
        }
        #endregion
        public static AnimalComparer GetComparer()
        {
            return new Animal.AnimalComparer();
        }
        public int CompareTo(Animal rhs,
            Animal.AnimalComparer.ComparisonType which)
        {
            switch (which)
            {
                case AnimalComparer.ComparisonType.Weght:
                    return this.weight.CompareTo(rhs.weight);
                case AnimalComparer.ComparisonType.Name:
                    return this.name.CompareTo(rhs.name);
                default:
                    return 0;
            }
        }
        public class AnimalComparer : IComparer<Animal>
        {
            public enum ComparisonType
            {
                Weght, Name,
            };
            private Animal.AnimalComparer.ComparisonType
                whichComparison;
            public Animal.AnimalComparer.ComparisonType
                WhichComparison
            {
                get { return whichComparison; }
                set { whichComparison = value; }
            }
            public int Compare(Animal lhs, Animal rhs)
            {
                return lhs.CompareTo(rhs, WhichComparison);
            }
            public bool Equals(Animal lhs, Animal rhs)
            {
                return this.Compare(lhs, rhs) == 0;
            }
        }
    }
    class Cat : Animal
    {
        public Cat(int weight, string name)
            : base(weight, name) { }
        public override void Speak()
        {
            Console.WriteLine("ニャーニャー");
        }
        public override void Move()
        {
            Console.WriteLine("するする");
        }
    }
    class Dog : Animal
    {
        public Dog(int weight, string name)
            : base(weight, name) { }
        public override void Speak()
        {
            Console.WriteLine("ワンワン");
        }
        public override void Move()
        {
            Console.WriteLine("てくてく");
        }
    }
    class Tester
    {
        void Display(List<Animal> animalList)
        {
            foreach (Animal animal in animalList)
            {
                Console.WriteLine(animal.ToString());
            }
        }
        public void Run()
        {
            Cat tama = new Cat(10, "Tama");
            Cat sora = new Cat(20, "Sora");
            Dog frisky = new Dog(15, "Frisky");
            Dog laika = new Dog(25, "Laika");
            Animal.AnimalComparer c = Animal.GetComparer();
            Animal[] animals = { tama, sora, frisky, laika };
            List<Animal> animalList = new List<Animal>();
            foreach (Animal animal in animals)
            {
                animalList.Add(animal);
            }
            Console.WriteLine("List");
            Display(animalList);
            Console.WriteLine("重さでソート");
            c.WhichComparison = Animal.AnimalComparer.ComparisonType.Weght;
            animalList.Sort(c);
            Display(animalList);
            Console.WriteLine("名前でソート");
            c.WhichComparison = Animal.AnimalComparer.ComparisonType.Name;
            animalList.Sort(c);
            Display(animalList);
        }
        static void Main()
        {
            Tester t = new Tester();
            t.Run();
        }
    }
}

入出力結果(Console Window)

List
Name: Tama Weight: 10
Name: Sora Weight: 20
Name: Frisky Weight: 15
Name: Laika Weight: 25
重さでソート
Name: Tama Weight: 10
Name: Frisky Weight: 15
Name: Sora Weight: 20
Name: Laika Weight: 25
名前でソート
Name: Frisky Weight: 15
Name: Laika Weight: 25
Name: Sora Weight: 20
Name: Tama Weight: 10
続行するには何かキーを押してください . . .