C# - Xamarin - 継承 - オブジェクトの系図(ベースクラス、サブクラス、メソッドの上書き、virtualキーワード、overrideキーワード)

Head First C#
原著

開発環境

• OS: Windows 10 Pro
• IDE(統合開発環境): Visual Studio Community 2017

Head First C# ―頭とからだで覚えるC#の基本 (Andrew Stellman (著)、Jennifer Greene (著)、佐藤 嘉一 (監修, 監修)、木下 哲也 (翻訳)、オライリージャパン)の5章(継承 - オブジェクトの系図)、プールパズル(p. 199)を取り組んでみる。

コード

MainPage.xaml

<?xml version="1.0" encoding="utf-8" ?>
<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:App1"
             x:Class="App1.MainPage">

    <StackLayout>
        <!-- Place new controls here -->
        <!--
     <Label Text="Welcome to Xamarin.Forms!" 
           HorizontalOptions="Center"
           VerticalOptions="CenterAndExpand" />
        -->
    </StackLayout>

</ContentPage>

MainPage.xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;

namespace App1
{
    public partial class MainPage
    {
        public MainPage()
        {
            InitializeComponent();

            string xyz = "";
            Boat boat = new Boat();
            Sailboat sailboat = new Sailboat();
            Rowboat rowboat = new Rowboat();

            sailboat.setLength(32);
            xyz = boat.move();
            xyz += rowboat.move();
            xyz += sailboat.move();

            DisplayAlert("", xyz, "OK");
        }
    }

    public class Boat
    {
        private int length;

        public void setLength(int length)
        {
            this.length = length;
        }
        public int getLength()
        {
            return length;
        }
        public virtual string move()
        {
            return "ドリフト ";
        }
    }
    public class Rowboat:Boat
    {
        public string rowTheBoat()
        {
            return "ナターシャ、漕げ";
        }
    }
    public class Sailboat : Boat
    {
        public override string move()
        {
            return "帆を上げろ。";
        }
    }
}

App.xaml

<?xml version="1.0" encoding="utf-8" ?>
<Application xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             x:Class="App1.App">
    <Application.Resources>
        
    </Application.Resources>
</Application>

App.xaml.cs

using System;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;

[assembly: XamlCompilation (XamlCompilationOptions.Compile)]
namespace App1
{
 public partial class App : Application
 {
  public App ()
  {
   InitializeComponent();

            // MainPage = new MainPage();
            MainPage = new NavigationPage(
                new MainPage() { Title = "" });
  }

  protected override void OnStart ()
  {
   // Handle when your app starts
  }

  protected override void OnSleep ()
  {
   // Handle when your app sleeps
  }

  protected override void OnResume ()
  {
   // Handle when your app resumes
  }
 }
}