C#_intro

C#_intro

virtual method

In C#, a virtual method is a method that can be overridden in a derived class. When a method is declared as virtual in a base class, it allows a derived class to provide its own implementation of the method.

public class Animal
{
    public virtual void MakeSound()
    {
        Console.WriteLine("The animal makes a sound");
    }
}

public class Cat : Animal
{
    public override void MakeSound()
    {
        Console.WriteLine("The cat meows");
    }
}

Difference between Abstract: virtual method is optional to be override in subclass, but Abstract method must be overriden in subclass.

Operator overloading - predefined unary, arithmetic, equality and comparison operators

让运算符看起来更简洁

    public static Fraction operator +(Fraction a) => a;
    public static Fraction operator -(Fraction a) => new Fraction(-a.num, a.den);

    public static Fraction operator +(Fraction a, Fraction b)
        => new Fraction(a.num * b.den + b.num * a.den, a.den * b.den);

    public static Fraction operator -(Fraction a, Fraction b)
        => a + (-b);

    public static Fraction operator *(Fraction a, Fraction b)
        => new Fraction(a.num * b.num, a.den * b.den);


Apprentice  a = new Apprentice();
Apprentice  p1 = new Provision(10), p2 = new Provision(50);
Apprentice  newa = p1 + p2 + a;

indexer

https://learn.microsoft.com/zh-cn/dotnet/csharp/indexers

通过索引来访问对象

generic and refence an array

ref & out: 调用时必须填入可赋值的变量，且要加上对应的rer或out词缀. 修改方法内的rer和out变量，将会直接改变调用者外部填入的变量.

区别在于rer可以不修改，作为普通参数使用，out则必须修改，且在修改后才能在方法内使用 可以通过定义多个rer或out参数，来实现一个方法带出多个返回值

// list, Dictionary, Stack, Queue 封装好的 支持泛型 的存储数据结构
// 非泛型 -> hashtable
void AddElenment<Type> (ref Type[] array Type newElement)
    {
        Type[] new Array = new Type[array.Length + 1];
    }

// var -> unsure the value type in the generic data structure
    foreach (var item in playerInfo)

delegate

“Delegate是一个可以存放函数的容器”

如果把所有方法放到各个不同的类里，另一个类要应用就要新建一个instance来引用，很复杂。所以新建一个Event作为委托类，所有的类需要的方法都从这个Event类里来引用。

class commend
{
    // 定义一个delegate
public delegate void Event(string s);

// 创建delegate
// weather 和 notice可以 commend.weather来引用
Event weather, notice;

void Start(){
    weather("sunny");
    // weather += GoToLib;
    weather += (s) => {print("今天" + s);};
}
// commend.weather 一次运行所有被+=的functions
void GoTolib(string s) {};
    print("今天" + s);
}

Action

类似于 unity event

using UnityEngine.Events;
[System.Serializable]
public class EventVector3 : UnityEvent<Vector3> { }
public class MouseManager : MonoBehaviour
{
        public EventVector3 OnMouseClicked;
}

    public static Action<int> test;

    private void Start()
    {
        // bind the method
        Event.test += num =>
        {
            print(num + "\n" + (num + 1) + "\n" + "hello");
        };

        // invoke the method
        for (int i = 0; i < 5; i++)
        {
            Event.test?.Invoke(i);
        }
    }

enum

默认情况下，枚举成员的关联常数值为类型 int；它们从零开始，并按定义文本顺序递增 1。 可以显式指定任何其他整数数值类型作为枚举类型的基础类型。

Property - get / set

    public CharacterStats_SO characterData;
    #region Read from Data_SO
    public int MaxHealth
    {
        get
        {
            if (characterData != null)
            {
                return characterData.maxHealth;
            }
            else
            {
                return 0;
            }
        }
        set
        {
            characterData.maxHealth = value;
        }
    }

Extention

eg. make a extension to Transform

public static class ExtensionMethod
{
    private const float dotThreshold = 0.5f;
    public static bool IsFacingTarget(this Transform transform, Transform target)
    {
        var vectorToTarget = target.position - transform.position;
        vectorToTarget.Normalize();

        float dot = Vector3.Dot(transform.up, vectorToTarget);
        return dot >= dotThreshold;
    }
}

ToString

    private void Update()
    {
        levelText.text = "Level " + GameManager.Instance.playerStats.characterData.currentLevel.ToString("00");
        UpdateHealth();
        UpdateExp();
    }

Property

    public InventoryData_SO Bag { get; set; }

    public int Index {get; set;} = -1;

LINQ 查询操作

    public List<QuestTask> tasks = new List<QuestTask>();

    public bool HaveQuest(QuestData_SO data)
    {
        if (data != null)
        {
            return tasks.Any(q => q.questData.questName == data.questName);
        }
        else
        {
            return false;
        }
    }

    public QuestTask GetTask(QuestData_SO data)
    {
        return tasks.Find(q => q.questData.questName == data.questName);
    }