C# - ジェネリックとコレクション(List、IComparable インターフェース、ソート方法の制御、IComparerインターフェース、Compare メソッド、enum(列挙型))

初めてのC# 第2版
原著

開発環境

• OS: macOS High Sierra - Apple
• IDE(統合開発環境): Visual Studio for Mac
• プログラミング言語: C#

初めてのC# 第2版 (Jesse Liberty (著)、Brian MacDonald (著)、日向 俊二 (翻訳)、オライリージャパン)の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.を取り組んでみる。

コード

using System;
using System.Collections.Generic;

namespace sample14_1
{
    abstract class Animal : IComparable<Animal>
    {
        private int weight;
        private string name;
        public Animal(int weight, string name)
        {
            this.weight = weight;
            this.name = name;
        }
        abstract public void Speak();
        abstract public void Move();

        public override string ToString()
        {
            return String.Format("Name: {0}, Weight: {1}", name, weight);
        }
        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>
        {
            public enum ComparisonType
            {
                Weight,
                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);
            }
        }
    }
    class Cat : Animal
    {
        public Cat(int weight, string name) : base(weight, name) { }
        public override void Speak()
        {
            Console.WriteLine("にゃーにゃー");
        }
        public override void Move()
        {
            Console.WriteLine("スルスル");
        }
        public override string ToString()
        {
            return string.Format("[Cat] {0}", base.ToString());
        }
    }
    class Dog : Animal
    {

        public Dog(int weight, string name) : base(weight, name) { }
        public override void Speak()
        {
            Console.WriteLine("わんわん");
        }
        public override void Move()
        {
            Console.WriteLine("テクテク");
        }
        public override string ToString()
        {
            return string.Format("[Dog] {0}", base.ToString());
        }
    }
    class Program
    {
        static void Display(List<Animal> animals)
        {
            foreach (var animal in animals)
            {
                Console.WriteLine(animal);
            }
        }
        static void Main(string[] args)
        {
            Cat cat1 = new Cat(10, "cat1");
            Cat cat2 = new Cat(30, "cat2");
            Dog dog1 = new Dog(20, "dog1");
            Dog dog2 = new Dog(40, "dog2");
            Animal[] animals = { cat1, cat2, dog1, dog2 };
            Animal.AnimalComparer c = new Animal.AnimalComparer();

            List<Animal> animalList = new List<Animal>();
            foreach (var animal in animals)
            {
                animalList.Add(animal);
            }
            Display(animalList);
            Console.WriteLine("Default");
            animalList.Sort();
            Display(animalList);
            Console.WriteLine("Name");
            c.WhichComparison = Animal.AnimalComparer.ComparisonType.Name;
            animalList.Sort(c);
            Display(animalList);
            Console.WriteLine("Weight");
            c.WhichComparison = Animal.AnimalComparer.ComparisonType.Weight;
            animalList.Sort(c);
            Display(animalList);
        }
    }
}

入出力結果(Terminal)

[Cat] Name: cat1, Weight: 10
[Cat] Name: cat2, Weight: 30
[Dog] Name: dog1, Weight: 20
[Dog] Name: dog2, Weight: 40
Default
[Cat] Name: cat1, Weight: 10
[Dog] Name: dog1, Weight: 20
[Cat] Name: cat2, Weight: 30
[Dog] Name: dog2, Weight: 40
Name
[Cat] Name: cat1, Weight: 10
[Cat] Name: cat2, Weight: 30
[Dog] Name: dog1, Weight: 20
[Dog] Name: dog2, Weight: 40
Weight
[Cat] Name: cat1, Weight: 10
[Dog] Name: dog1, Weight: 20
[Cat] Name: cat2, Weight: 30
[Dog] Name: dog2, Weight: 40

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