C# - ジェネリックとコレクション(インターフェース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)14.5(練習問題)練習14-4を解いてみる。

その他参考書籍

• プログラミングC# 第6版

練習14-4.

コード

using System;
using System.Collections.Generic;

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 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 AnimalComparer.ComparisonType.Weight:
                return this.weight.CompareTo(rhs.weight);
            case AnimalComparer.ComparisonType.Name:
                return this.name.CompareTo(rhs.name);
            default:
                return 0;
        }
    }
    public class AnimalComparer : IComparer<Animal>
    {
        private Animal.AnimalComparer.ComparisonType
            whichComparison;
        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);
        }
        public Animal.AnimalComparer.ComparisonType WhichComparison
        {
            get { return whichComparison; }
            set { whichComparison = value; }
        }
    }
}

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 Display(List<Animal> animalList)
    {
        foreach (Animal animal in animalList)
        {
            Console.WriteLine(animal.ToString());
        }
    }
    public void Run()
    {
        Cat tama = new Cat(5, "Tama");
        Cat sora = new Cat(15, "Sora");
        Dog pochi = new Dog(10, "Pochi");
        Dog taro = new Dog(20, "Taro");
        Animal[] animals = { tama, sora, pochi, taro };
        List<Animal> animalList = new List<Animal>();
        foreach (Animal animal in animals)
        {
            animalList.Add(animal);
        }
        Console.WriteLine("動物のリスト");
        Display(animalList);
        Animal.AnimalComparer c = Animal.GetComparer();
        Console.WriteLine("重さでソート");
        c.WhichComparison = Animal.AnimalComparer.ComparisonType.Weight;
        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)

動物のリスト
Name: Tama, Weight: 5
Name: Sora, Weight: 15
Name: Pochi, Weight: 10
Name: Taro, Weight: 20
重さでソート
Name: Tama, Weight: 5
Name: Pochi, Weight: 10
Name: Sora, Weight: 15
Name: Taro, Weight: 20
名前でソート
Name: Pochi, Weight: 10
Name: Sora, Weight: 15
Name: Tama, Weight: 5
Name: Taro, Weight: 20
続行するには何かキーを押してください . . .