C# - ジェネリックとコレクション(インタフェースIComparer<T>の実装)

初めてのC# 第2版
Jesse Liberty (著) Brian MacDonald (著)
日向俊二 (訳)
原書: Learning C# 2005

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;
        }
        public bool Equals(Animal other)
        {
            if (this.weight == other.weight)
            {
                return true;
            }
            return false;
        }
        public static AnimalComparer GetComparer()
        {
            return new Animal.AnimalComparer();
        }
        public int CompareTo(Animal rhs)
        {
            return this.weight.CompareTo(rhs.weight);
        }
        public int CompareTo(Animal rhs,
            Animal.AnimalComparer.ComparisonType which)
        {
            switch (which)
            {
                case Animal.AnimalComparer.ComparisonType.weight:
                    return this.weight.CompareTo(rhs.weight);
                case Animal.AnimalComparer.ComparisonType.name:
                    return this.name.CompareTo(rhs.name);
                default:
                    return 0;
            }
        }

        public class AnimalComparer : IComparer<Animal>
        {
            private Animal.AnimalComparer.ComparisonType
                whichComparison;
            public Animal.AnimalComparer.ComparisonType WhichComparison
            {
                get { return whichComparison; }
                set { whichComparison = value; }
            }
            public enum ComparisonType
            {
                weight, name,
            };
            public bool Equals(Animal lhs, Animal rhs)
            {
                return this.Compare(lhs, rhs) == 0;
            }
            public int Compare(Animal lhs, Animal rhs)
            {
                return lhs.CompareTo(rhs, WhichComparison);
            }
        }
    }
    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
    {
        public void P(List<Animal> list)
        {
            foreach (Animal animal in list)
            {
                Console.WriteLine(animal);
            }
        }
        public void Run()
        {
            Dog pochi = new Dog(10, "Pochi");
            Dog laika = new Dog(20, "Laika");
            Dog taro = new Dog(25, "Taro");
            Cat tama = new Cat(15, "Tama");
            Cat sora = new Cat(25, "Sora");
            Cat ctaro = new Cat(20, "Taro");
            Animal[] animals = { pochi, laika, taro, tama, sora, ctaro };
            List<Animal> animalList = new List<Animal>();
            foreach (Animal a in animals)
            {
                animalList.Add(a);
            }
            Console.WriteLine("動物のリスト");
            P(animalList);
            Console.WriteLine("名前でソート");
            Animal.AnimalComparer c = Animal.GetComparer();
            c.WhichComparison = Animal.AnimalComparer.ComparisonType.name;
            animalList.Sort(c);
            P(animalList);
            Console.WriteLine("重さでソート");
            c.WhichComparison = Animal.AnimalComparer.ComparisonType.weight;
            animalList.Sort(c);
            P(animalList);
        }
        static void Main()
        {
            Tester t = new Tester();
            t.Run();
        }
    }
}

入出力結果(Console Window)

動物のリスト
Name: Pochi, Weight: 10
Name: Laika, Weight: 20
Name: Taro, Weight: 25
Name: Tama, Weight: 15
Name: Sora, Weight: 25
Name: Taro, Weight: 20
名前でソート
Name: Laika, Weight: 20
Name: Pochi, Weight: 10
Name: Sora, Weight: 25
Name: Tama, Weight: 15
Name: Taro, Weight: 20
Name: Taro, Weight: 25
重さでソート
Name: Pochi, Weight: 10
Name: Tama, Weight: 15
Name: Taro, Weight: 20
Name: Laika, Weight: 20
Name: Taro, Weight: 25
Name: Sora, Weight: 25
続行するには何かキーを押してください . . .