C#初心者を卒業しよう(第3回の解答例)

プログラム

Program.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
builder.Services
    .AddTransient<DistanceService>()
    .AddScoped<IToYards, ToYards>()
    .AddScoped<IToMeters, ToMeters>()
    .AddScoped<IMetersToFeet, MetersToFeet>()
    .AddScoped<IFeetToMeters, FeetToMeters>();
using IHost host = builder.Build();

var service = host.Services.GetService<DistanceService>() ??
    throw new NotImplementedException(
        "Faild to create 'DistanceService' object.");
service.Run();

public interface IDistance
{
    void Calculate(double distance);
    string CreateAnswerMessage();
}

public class DistanceService(IServiceProvider serviceProvider)
{
    public void Run()
    {
        var convertNumber = InputConvertNumber();
        var distanceObject = Create(convertNumber) ??
            throw new NotImplementedException(
                "Faild to create 'IDistance' object.");

        var distance = InputDistance();
        distanceObject.Calculate(distance);

        OutputAnswer(distanceObject);
    }

    protected virtual int InputConvertNumber()
    {
        Console.WriteLine("Please input convert number.");
        Console.WriteLine("1 : Convert meters to yards.");
        Console.WriteLine("2 : Convert yards to meters.");
        Console.WriteLine("3 : Convert meters to feet.");
        Console.WriteLine("4 : Convert feet to meters.");
        if (int.TryParse(Console.ReadLine(), out var convertNumber))
        {
            return convertNumber;
        }
        throw new FormatException("Invalid input convert number.");
    }

    protected virtual IDistance? Create(int convertNumber)
    {
        switch (convertNumber)
        {
            case 1:
                return (IDistance?)serviceProvider.GetService(typeof(IToYards));
            case 2:
                return (IDistance?)serviceProvider.GetService(typeof(IToMeters));
            case 3:
                return (IDistance?)serviceProvider.GetService(typeof(IMetersToFeet));
            case 4:
                return (IDistance?)serviceProvider.GetService(typeof(IFeetToMeters));
            default:
                throw new ArgumentOutOfRangeException(
                    $"{convertNumber} is out of range.");
        }
    }

    protected virtual double InputDistance()
    {
        Console.WriteLine("Please input distance.");
        if (double.TryParse(Console.ReadLine(), out var distance))
        {
            return distance;
        }
        throw new FormatException("Invalid input distance.");
    }

    protected virtual void OutputAnswer(IDistance distance)
    {
        var outputMessage = distance.CreateAnswerMessage();
        Console.WriteLine(outputMessage);
    }
}

public interface IToYards : IDistance
{
}

public class ToYards : IToYards
{
    private double _yards;
    private double _meters;

    public void Calculate(double meters)
    {
        _meters = meters;
        _yards = meters * 1.0936133d;
    }

    public string CreateAnswerMessage()
    {
        return $"{_meters} meters is {_yards} yards.";
    }
}

public interface IToMeters : IDistance
{
}

public class ToMeters : IToMeters
{
    private double _yards;
    private double _meters;

    public void Calculate(double yards)
    {
        _yards = yards;
        _meters = yards / 1.0936133d;
    }

    public string CreateAnswerMessage()
    {
        return $"{_yards} yards is {_meters} meters.";
    }
}

public interface IMetersToFeet : IDistance
{
}

public class MetersToFeet : IMetersToFeet
{
    private double _feet;
    private double _meters;

    public void Calculate(double meters)
    {
        _meters = meters;
        _feet = meters / 0.3048d;
    }

    public string CreateAnswerMessage()
    {
        return $"{_meters} meters is {_feet} feet.";
    }
}

public interface IFeetToMeters : IDistance
{
}
public class FeetToMeters : IFeetToMeters
{
    private double _feet;
    private double _meters;

    public void Calculate(double feet)
    {
        _feet = feet;
        _meters = feet * 0.3048d;
    }

    public string CreateAnswerMessage()
    {
        return $"{_feet} feet is {_meters} meters.";
    }
}

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Answer03.zip

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ファイルダウンロードについて

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解説

　今回は前回と一部異なります。

入力メッセージを追加

　ここは問題ありませんね。

Console.WriteLine("3 : Convert meters to feet.");
Console.WriteLine("4 : Convert feet to meters.");

オブジェクト生成を追加

　オブジェクト生成部分を追加します。ここは少し違いますね。

public class DistanceFactory
{
    public static IDistance Create(int convertNumber)
    {
        switch (convertNumber)
        {
            case 1:
                return (IDistance?)serviceProvider
                    .GetService(typeof(IToYards));
            case 2:
                return (IDistance?)serviceProvider
                    .GetService(typeof(IToMeters));
            case 3:
                return (IDistance?)serviceProvider
                    .GetService(typeof(IMetersToFeet));
            case 4:
                return (IDistance?)serviceProvider
                    .GetService(typeof(IFeetToMeters));
            default:
                throw new ArgumentOutOfRangeException(
                    $"{convertNumber} is out of range.");
        }
    }
}

変換クラスを追加

　メートルをフィートに変換するインターフェースとクラスを追加します。

public interface IMetersToFeet : IDistance
{
}

public class MetersToFeet : IMetersToFeet
{
    private double _feet;
    private double _meters;

    public void Calculate(double meters)
    {
        _meters = meters;
        _feet = meters / 0.3048;
    }

    public string CreateAnswerMessage()
    {
        return $"{_meters} meters is {_feet} feet.";
    }
}

　フィートをメートルに変換するインターフェースとクラスを追加します。

public interface IFeetToMeters : IDistance
{
}

public class FeetToMeters : IFeetToMeters
{
    private double _feet;
    private double _meters;

    public void Calculate(double feet)
    {
        _feet = feet;
        _meters = feet * 0.3048;
    }

    public string CreateAnswerMessage()
    {
        return $"{_feet} feet is {_meters} meters.";
    }
}

DI コンテナに登録

　最後に DI コンテナに登録します。これを忘れないように。

HostApplicationBuilder builder = Host.CreateApplicationBuilder(args);
builder.Services
    .AddTransient<DistanceService>()
    .AddScoped<IToYards, ToYards>()
    .AddScoped<IToMeters, ToMeters>()
    .AddScoped<IMetersToFeet, MetersToFeet>()
    .AddScoped<IFeetToMeters, FeetToMeters>();

using IHost host = builder.Build();