C# with Godot：物以类聚

GDScript中的类

class_name Player

var player: Player

C#中的类定义

• 类就是一个模子，对象就是从这个模子里倒出来的具体的东西
• 类是状态（数据）和行为（方法）的封装（encapsulation），这些行为会改变类的状态

class Player {}

类和源文件不是一对一关系

源文件里可以写些啥

命名空间

namespace MyProject;

命名空间的嵌套

namespace UI
{
    class Foo{}
}
namespace UI.Components
{
    class Bar
    {
        Foo foo;
    }
}

省略命名空间

System.Text.Json.JsonSerializer.Serialize

using System.Text.Json;

new一个对象

Player player = new Player();

var p = new Player(); // 用var声明变量
Player pp = new(); // pp声明为Player类型，调用构造函数时省略类名
var p = new(); // 错误！

字段

class Player
{
    int id;
    string name;
}

var p = new Player();
p.id = 1;

访问级别

private int id;

静态字段

Console.WriteLine(Player.playerCount);
​
class Player
{
    public int id;
    public string name;
    public static int playerCount;
}

构造函数

class Player
{
    public int id;
    public string name;
    
    public Player(int id, string name)
    {
        this.id = id;
        this.name = name;
    }
}

这个

初始化

class Player
{
    public int id = -1;
    public string name = "Anonymous";
    // ...
}

多个构造函数

class Player
{
    public int id;
    public string name;
    public static int playerCount = 0;
    
    public Player(string name)
    {
        this.id = playerCount++;
        this.name = name;
    }
    
    public Player(int id, string name)
    {
        this.id = id;
        this.name = name;
    }
}

方法

class Player
{
    // 省略字段定义
    public void Greet()
    {
        Console.WriteLine($"Hello! I'm {name}!");
    }
}

静态方法

方法重载

静态类

属性——封装字段

// Player的定义中
// 假设id和name为private的字段
public int GetId() => id;
public void SetName(string newName)
{
    Console.WriteLine($"Player {id} changed name from {name} to {newName}");
    name = newName;
}
public string GetName() => name;

var name: String:
    set(value):
        name = value
    get:
        return name

private string name;
public string Name
{
    get
    {
        return name;
    }
    set
    {
        Console.WriteLine($"Player {id} changed name from {name} to {value}");
        name = value;
    }
}

var p = new Player();
p.Name = "John";
Console.WriteLine(p.Name);

public string Name { set; get; }

public string Name { private set; get; }

public string Name { set; get; } = "Anonymous";

递归注意

var username: String = "name":
    set(value):
        print("set username")
        username = value
    get:
        print("get username")
        return username
​
func _ready() -> void:
    username = "Abc"
    print(username)

public string Username
{
    set(value) => Username = value;
    // 略
}

展望未来：消除backing field

public int Prop
{
    get;
    set
    {
        field = value;
    }
}

计算属性

class Circle
{
    public float Radius {private set;get;}
    public float Area => Radius * Radius * MathF.PI;
}

泛型类

class Box<T>
{
    private T value;
    public T Value => value;
    public Box<T>(T value)
    {
        this.value = value;
    }
}