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重写Equals与运算符"=="及二者区别_020

萧然 2018-09-13 1.4k浏览

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先说一下函数Equals和运算符"=="二者的区别:

1. 对比值类型:
”==“ 与 ”Equals“ 一样,都是对比变量值
C#已经重写了string的”==“和”Equals“,对比结果与值类型一致

2. 对比引用类型:
引用类型:内容存储在堆,堆地址存储在栈
”==“ 对比引用地址,即栈内存储的堆地址
”Equals“ 对比对象,即堆上存储的对象内容

举一个栗子来说明重写,需要的可以按此方式扩展啦~

一条2D线段,用起点终点来表示,判断线段相等需要判断起点终点都相等,这个比较简单,就不上代码啰嗦啦。重点是通过重写Equals函数,更方便的实现判断。

//定义线段类
class OverrideLine
{
    public Vector2 A { get; private set; }
    public Vector2 B { get; private set; }
    public OverrideLine(Vector2 pointA, Vector2 pointB)
    {
        A = pointA;
        B = pointB;
    }
    //比较自定义对象
    //重写Equals, 判断线段相等
    public override bool Equals(object obj)
    {
        if (obj is OverrideLine)
        {
            var edge = (OverrideLine)obj;
            return (edge.A == A && edge.B == B) || (edge.B == A && edge.A == B);
        }
        return false;
    }
    //重写了Equals函数,同时也必要重写GetHashCode函数
    //判断Equals时,两个对象的GetHashCode()返回值相等是且Equals()函数的必要条件
    //即:GetHashCode()返回值相等,且Equals()函数体内部逻辑返回值为true,则Equals()返回true
    //重写GetHashCode
    public override int GetHashCode()
    {
        return A.GetHashCode() ^ B.GetHashCode();
    }
    //重写==
    public static bool operator ==(OverrideLine line01, OverrideLine line02)
    {
        return line01.Equals(line02);
    }
    //运算符!=要与==一起重写
    public static bool operator !=(OverrideLine line01, OverrideLine line02)
    {
        return !(line01 == line02);
    }
    //
    //扩展,重写ToString,自定义Log输出的格式内容
    public override string ToString()
    {
        return string.Format("[" + A + "->" + B + "]");
    }
}

//在定义一个普通的类,以作对比
class NormalLine
{
    public Vector2 A { get; private set; }
    public Vector2 B { get; private set; }
    public NormalLine(Vector2 pointA, Vector2 pointB)
    {
        A = pointA;
        B = pointB;
    }
}

//接下来打印一下对比结果
public class Test: MonoBehaviour 
{
    void Start () 
    {
        OverrideLine line01 = new OverrideLine(Vector2.zero, Vector2.one);
        OverrideLine line02 = new OverrideLine(Vector2.zero, Vector2.one);
        List<OverrideLine> overrideLineList = new List<OverrideLine>();
        overrideLineList.Add(line01);
        Debug.Log(line01.Equals(line02));       //true
        Debug.Log(line01 == line02);        //true
        Debug.Log(overrideLineList.Contains(line02));    //true
        NormalLine line03 = new NormalLine(Vector2.zero, Vector2.one);
        NormalLine line04 = new NormalLine(Vector2.zero, Vector2.one);
        List<NormalLine> normalLineList = new List<NormalLine>();
        normalLineList.Add(line03);
        Debug.Log(line03.Equals(line04));     //false
        Debug.Log(line03 == line04);     //false
        Debug.Log(normalLineList.Contains(line04));     //false
    }
}