1.什麼是運算子過載
定義:(百科定義)就是把已經定義的、有一定功能的操作符進行重新定義,來完成更為細緻具體的運算等功能。操作符過載可以將概括性的抽象操作符具體化,便於外部呼叫而無需知曉內部具體運算過程。
2.為什麼需要運算子過載?
在C#中 ,內建的資料型別有:int、double等這些型別是預先在系統內定義好的,可以直接進行數值加減運算。例如:int i, j = 1; int sum=i+j;可以直接得到想要的和sum。
如果要比較一個類(結構)進行物件比較加、減等操作 該如何實現?例如一個類Box,有物件Box1和Box2,那麼, 如何實現物件相加Box3 = Box1 + Box2?
這時,我們就要用到具有使用者定義型別的運算子。過載運算子是具有特殊名稱的功能,關鍵字operator
後跟定義運算子的符號。 類似於任何其他函式定義,過載運算子具有返回型別和引數列表。
3.下面用三個案例,以逐步步進的方式解析一下
1 namespace operator_overload 2 { 3 class Program 4 { 5 static void Main(string[] args) 6 { 7 Box Box1 = new Box(); 8 Box Box2 = new Box(); 9 Box Box3 = new Box(); 10 11 double volume1,volume2 = 0.0; 12 13 Box1.setLength(60.0); 14 Box1.setBreadth(70.0); 15 Box1.setHeight(50.0); 16 17 Box2.setLength(121.0); 18 Box2.setBreadth(133.0); 19 Box2.setHeight(110.0); 20 21 volume1 = Box1.getVolume(); 22 Console.WriteLine("Volume of Box1 :{0}",volume1); 23 24 volume2 = Box2.getVolume(); 25 Console.WriteLine("Volume of Box1 :{0}", volume2); 26 27 28 } 29 } 30 31 class Box 32 { 33 private double length; 34 private double breadth; 35 private double height; 36 37 public double getVolume() 38 { 39 return length * breadth * height; 40 } 41 public void setLength(double len) 42 { 43 length = len; 44 } 45 public void setBreadth(double bre) 46 { 47 breadth = bre; 48 } 49 public void setHeight(double hei) 50 { 51 height = hei; 52 } 53 54 }
案例一沒有運用運算子過載,也沒類或結構相加,可以正常求和;
1 namespace operator_overload 2 { 3 class Program 4 { 5 static void Main(string[] args) 6 { 7 Box Box1 = new Box(); 8 Box Box2 = new Box(); 9 Box Box3 = new Box(); 10 11 double volume1,volume2 = 0.0; 12 13 Box1.setLength(60.0); 14 Box1.setBreadth(70.0); 15 Box1.setHeight(50.0); 16 17 Box2.setLength(121.0); 18 Box2.setBreadth(133.0); 19 Box2.setHeight(110.0); 20 21 volume1 = Box1.getVolume(); 22 Console.WriteLine("Volume of Box1 :{0}",volume1); 23 24 volume2 = Box2.getVolume(); 25 Console.WriteLine("Volume of Box1 :{0}", volume2); 26 27 Box3 = Box1 + Box2; //類例項進行相加; 28 } 29 } 30 31 class Box 32 { 33 private double length; 34 private double breadth; 35 private double height; 36 37 public double getVolume() 38 { 39 return length * breadth * height; 40 } 41 public void setLength(double len) 42 { 43 length = len; 44 } 45 public void setBreadth(double bre) 46 { 47 breadth = bre; 48 } 49 public void setHeight(double hei) 50 { 51 height = hei; 52 } 53 54 55 } 56 } 57 }
案例二,增加了“Box3 = Box1 + Box2;”,但是沒有相應的運算子程式碼進行支援,所以編譯器顯示如下提示
錯誤 1 運算子“+”無法應用於“operator_overload.Box”和“operator_overload.Box”型別的運算元
1 using System; 2 using System.Collections.Generic; 3 using System.Linq; 4 using System.Text; 5 6 namespace operator_overload 7 { 8 class Program 9 { 10 static void Main(string[] args) 11 { 12 Box Box1 = new Box(); 13 Box Box2 = new Box(); 14 Box Box3 = new Box(); 15 16 double volume,volume1,volume2 = 0.0; 17 18 Box1.setLength(60.0); 19 Box1.setBreadth(70.0); 20 Box1.setHeight(50.0); 21 22 Box2.setLength(121.0); 23 Box2.setBreadth(133.0); 24 Box2.setHeight(110.0); 25 26 volume1 = Box1.getVolume(); 27 Console.WriteLine("Volume of Box1 :{0}",volume1); 28 29 volume2 = Box2.getVolume(); 30 Console.WriteLine("Volume of Box1 :{0}", volume2); 31 32 Box3 = Box1 + Box2; 33 34 volume = Box3.getVolume(); 35 Console.WriteLine("Volume of Box3 :{0}", volume); 36 Console.ReadKey(); 37 } 38 } 39 40 class Box 41 { 42 private double length; 43 private double breadth; 44 private double height; 45 46 public double getVolume() 47 { 48 return length * breadth * height; 49 } 50 public void setLength(double len) 51 { 52 length = len; 53 } 54 public void setBreadth(double bre) 55 { 56 breadth = bre; 57 } 58 public void setHeight(double hei) 59 { 60 height = hei; 61 } 62 63 public static Box operator +(Box b, Box c) 64 { 65 Box box = new Box(); 66 box.length = b.length + c.length; 67 box.breadth = b.breadth + c.breadth; 68 box.height = b.height + c.height; 69 return box; 70 } 71 } 72 }
案例三,增加如下運算子過載的支撐程式碼
public static Box operator +(Box b, Box c) { Box box = new Box(); box.length = b.length + c.length; box.breadth = b.breadth + c.breadth; box.height = b.height + c.height; return box; }
Box類,Box3 = Box1 + Box2;對應的計算運算式如下:
5878880 = (60+121)*(70+133)*(50+110)
以上案例成功實現了類的相加!