隱式轉換 & 顯示轉換(強制轉換)
隱式轉換
- 隱式類型轉換：將取值範圍外小的值，裝到一個取值範圍較大的變量裡面，叫做隱式。
例如，int的值裝到float裡：float a = 5;、float的變量裝到double裡：double b = 1.25f;。
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| float a = 5; //int的值裝到float變量裡
double b = 1.25f; //float的值裝到doublel變量裡
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顯示轉換(強制轉換)
- 顯式類式轉換(強制轉換)：將取值範圍較大的值，裝到取值範圍較小的變量裡。
例如，將float的值裝到int裡肯定會報錯，所以咱們要明顯的告訴編譯器說，我這加個括號裡面放int(int)，我呢希望能夠把這個1.5給我強制轉換成一個int型的數字整數，放到變數c裡面去。
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| //int c = 1.5f; //會報錯
int c = (int)1.5f; //顯示轉換
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類型轉換運算符
C#允許將「顯式類型轉換」與「隱式類型轉換」看做運算符，並且得到「重載」功能
舉例：
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| class Person {
public int age = 0;
}
...
Person person = 12; //可否將int類型的12轉換為Person 呢？
int a = (int)Person; //可否將person類型強制轉換為int呢？
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格式
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| //隱式類型轉換
public static implicit operator 目標類型(類型 待轉換對象);
//顯式類型轉換
public static explicit operator 目標類型(類型 待轉換對象);
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舉例
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| class Person {
public int age = 0;
//隱式類型轉換
public static implicit operator Person(int age) {
Console.Write("implicit Person");
return new Person { age = age; }
}
//顯示類型轉換
public static explicit operator int(Person person) {
Console.Write("explicit Person");
return person.age;
}
}
//使用
Person person = 12; //隱式類型轉換
int a =(int)person; //顯示類型轉換
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練習
目標 1：Person p = 12, 隱式轉換
數值轉換為物件
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| class Person {
public int age = 0;
public string name = "default";
//目標1：Person p = 12, 隱式轉換
public static implicit operator Person(int age) {
//Person p = new Person();
//p.age = age;
//return p;
return new Person { age = age };
}
}
Person p = 12;
Console.WriteLine(p.age); //12
Console.WriteLine(p.name);//default
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目標 2: Person p = “Rii”;
字串轉換為物件
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| class Person {
public int age = 0;
public string name = "default";
//目標2: Person p = "Rii";
public static implicit operator Person(string name) {
return new Person { name = name };
}
}
Person p = "Rii";
Console.WriteLine(p.age); //0
Console.WriteLine(p.name);//Rii
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目標 3: Person p = “12”; 數字字串
年齡為字串
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| class Person {
public int age = 0;
public string name = "default";
//目標1：Person p = 12, 隱式轉換
public static implicit operator Person(string age) {
return new Person { age = Convert.ToInt32(age) };
}
}
Person p = 12;
Console.WriteLine(p.age); //12
Console.WriteLine(p.name);//default
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目標 4: int age = (int)p; //p 是person類型的對象
將物件「顯示轉換」放到int中
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| class Person {
public int age = 0;
public string name = "default";
//目標4: int age = (int)p; //p 是person類型的對象
public static explicit operator int(Person person) {
return person.age;
}
}
Person p = new Person();
p.age = 100;
int age = (int)p; //顯示轉換(強制轉換)
Console.WriteLine(age); //100
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目標 5: int age = p;//p 是person類型的對象
將物件「隱式轉換」放到int中
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| class Person {
public int age = 0;
public string name = "default";
//目標5: int age = p; //p 是person類型的對象
public static implicit operator int(Person person) {
return person.age;
}
}
Person p = new Person();
p.age = 100;
int age = p; //隱式轉換
Console.WriteLine(age); //100
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完整程式碼
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| class Person {
public int age = 0;
public string name = "default";
//目標1：Person p = 12, 隱式轉換
public static implicit operator Person(int age) {
//Person p = new Person();
//p.age = age;
//return p;
return new Person { age = age };
}
//目標2: Person p = "Rii";
//public static implicit operator Person(string name)
//{
// //Person p = new Person();
// //p.name = name;
// //return p;
// return new Person { name = name };
//}
//目標3: Person p = "12"; 數字字串
public static implicit operator Person(string age) {
int numAge = Convert.ToInt32(age);
return new Person { age = numAge };
}
//目標4: int age = (int)p; //p 是person類型的對象
//int age = p;
//public static explicit operator int(Person person) {
// return person.age;
//}
//目標5: int age = p;//p 是person類型的對象
public static implicit operator int(Person person) {
return person.age;
}
}
class Box {
public int width = 0;
public int height = 0;
public int depth = 0;
//重載+運算符
public static Box operator+(Box left, Box right) {
Box box = new Box();
box.width = left.width + right.width;
box.height = left.height + right.height;
box.depth = left.depth + right.depth;
return box;
}
//重載-運算符
public static Box operator-(Box left, Box right)
{
Box box = new Box();
box.width = left.width - right.width;
box.height = left.height - right.height;
box.depth = left.depth - right.depth;
return box;
}
}
class Vector {
public int x = 0;
public int y = 0;
//實現雙目運算符-減法
public static Vector operator -(Vector v1, Vector v2) {
Vector v = new Vector();
v.x = v1.x - v2.x;
v.y = v1.y - v2.y;
return v;
}
//實現單目運算符取反-
public static Vector operator -(Vector v) {
Vector nv = new Vector();
nv.x = -v.x;
nv.y = -v.y;
return nv;
}
//單目運算符中的 ++/--(只能二擇一)
//a++: 後++，先參與表達式運算，再加1
//++a: 前++，先加1，再參與運算
//前++
public static Vector operator ++(Vector v) {
//傳進來的v 跟回傳回去給vplus的，是指向同一塊內存
v.x += 1;
v.y += 1;
return v;
}
}
internal class Program
{
static void Main(string[] args)
{
//顯式類型轉換實驗
Person p = new Person();
p.age = 100;
int age = p;
Console.WriteLine(age);
//int age = (int)p;
//Console.WriteLine(age);
//隱式類型轉換實驗
//Person p1 = 12;
////Person p2 = "Rii";
//Person p3 = "12";
//Console.WriteLine(p1.age); //12
//Console.WriteLine(p1.name);//default
////Console.WriteLine(p2.age);//0
////Console.WriteLine(p2.name);//Rii
//Console.WriteLine(p3.age);//0
//Console.WriteLine(p3.name);//Rii
////前++
//Vector vplus = new Vector();
//vplus.x = 8;
//vplus.y = 9;
//++vplus;
//Console.WriteLine(vplus.x);
//Console.WriteLine(vplus.y);
//Vector v = new Vector();
//v.x = 5;
//v.y = 4;
//Vector v1 = new Vector();
//v1.x = 2;
//v1.y = 2;
//Vector nv = -v;//取反
//Vector minusV = v - v1; //相減
//Console.WriteLine($"x ={minusV.x}");
//Console.WriteLine($"y ={minusV.y}");
//Box box1 = new Box();
//Box box2 = new Box();
//box1.width = 10;
//box1.height = 10;
//box1.depth = 10;
//box2.width = 20;
//box2.height = 20;
//box2.depth = 20;
////Box b = Box operator+(box1, box2);
////Box b = box1 + box2;
//Box b = box1 - box2;
//Console.WriteLine($"width: {b.width} height: {b.height} depth: {b.depth}");
}
}
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https://www.bilibili.com/video/BV1Bm4y1a7wb