const_cast

被const修飾的函數可以被訪問，但是不能被修改成員變量
const_cast可以去掉const

#include <iostream>
using namespace std;class FHello
{
public:FHello();void Init();/*const*/
private:int a;int b;float c;
};
FHello::FHello()
{a = 0;b = 10;c = 20.f;
}
void FHello::Init()/*const*/
{auto Hello_a = [&](){cout << a << endl;};auto Hello_b = [&]()->bool{cout << b << endl;return true;};Hello_a();if (bool bHello = Hello_b()){cout << "true" << endl;}else{cout << "false" << endl;}
}
int main()
{const FHello* HelloTest = new FHello();//HelloTest->Init();因為HelloTest被const修飾了而上面代碼中沒有用const修飾//用const_cast去掉constFHello* Test = const_cast<FHello*>(HelloTest);Test->Init();//編譯出錯會返回NULL//c風格的強轉，是萬能強轉//容易出問題，萬一轉換失敗了變成野指針了也不知道，少用FHello* NewTest = (FHello*)HelloTest;NewTest->Init();delete HelloTest;return 0;
}

reinterpret_cast

把指針轉換成int，也可以把int轉成指針，也可以指針轉換成指針

#include <iostream>
using namespace std;class FHello
{
public:FHello();void Init();/*const*/
private:int a;int b;float c;
};
FHello::FHello()
{a = 0;b = 10;c = 20.f;
}
void FHello::Init()/*const*/
{auto Hello_a = [&](){cout << a << endl;};auto Hello_b = [&]()->bool{cout << b << endl;return true;};Hello_a();if (bool bHello = Hello_b()){cout << "true" << endl;}else{cout << "false" << endl;}
}
int main()
{//const_castconst FHello* HelloTest = new FHello();FHello* Test = const_cast<FHello*>(HelloTest);Test->Init();FHello* NewTest = (FHello*)HelloTest;NewTest->Init();//reinterpret_cast//reinterpret_cast,先轉換成int，再轉換成指針int a = reinterpret_cast<int>(NewTest);FHello*b = reinterpret_cast<FHello*>(a);b->Init();//也可以轉換成int*指針，也可以轉換回來int* a2 = reinterpret_cast<int*>(NewTest);FHello* b2 = reinterpret_cast<FHello*>(a2);b2->Init();//可以轉換成float*指針，但是不可以用float類型float* a3 = reinterpret_cast<float*>(NewTest);FHello* b3 = reinterpret_cast<FHello*>(a3);b3->Init();delete HelloTest;return 0;
}

dynamic_cast

動態的轉化：可以向上轉化也可以向下轉化
向上轉化和向下轉化的意思是在數層的繼承關系中，可以向父類或派生類進行轉化
向下轉換時會進行類型檢測，如果類型無法轉換回返回NULL。是一個比較安全的轉換
接口（父類）必須有虛函數，否則會報錯

#include <iostream>
using namespace std;class FHello
{
public:FHello();virtual ~FHello();void Init();/*const*/
private:int a;int b;float c;
};
FHello::FHello()
{a = 0;b = 10;c = 20.f;
}
FHello::~FHello() {}
void FHello::Init()/*const*/
{auto Hello_a = [&](){cout << a << endl;};auto Hello_b = [&]()->bool{cout << b << endl;return true;};Hello_a();if (bool bHello = Hello_b()){cout << "true" << endl;}else{cout << "false" << endl;}
}class FHello1:public FHello
{
public:void Hello1temp() {}
private:int a;
};class FHello2 :public FHello1
{};int main()
{//const_castconst FHello* HelloTest = new FHello();FHello* Test = const_cast<FHello*>(HelloTest);Test->Init();FHello* NewTest = (FHello*)HelloTest;NewTest->Init();//reinterpret_castint a = reinterpret_cast<int>(NewTest);FHello*b = reinterpret_cast<FHello*>(a);b->Init();int* a2 = reinterpret_cast<int*>(NewTest);FHello* b2 = reinterpret_cast<FHello*>(a2);b2->Init();float* a3 = reinterpret_cast<float*>(NewTest);FHello* b3 = reinterpret_cast<FHello*>(a3);b3->Init();//dynamic_castFHello* h1 = new FHello1();//這一步也是向上轉換//向下轉換：FHello1* A = dynamic_cast<FHello1*>(h1);A->Hello1temp();//向上轉換,用的少，因為有更簡單的方法，如上FHello* B = dynamic_cast<FHello*>(A);B->Init();FHello* B2 = A;//進行隱式轉換FHello2* FHA2 = dynamic_cast<FHello2*>(h1);//轉換失敗，輸出NULLif (FHA2){}delete HelloTest;delete h1;return 0;
}

static_cast

可以向上轉化也可以向下轉化
向下轉換時不安全
static_cast不可以轉換const、volitale、_unaligned

static_cast和dynamic_cast相比static_cast可以沒有虛函數，而dynamic_cast必須有虛函數

格式

FHello* A=static_cast<FHello*>(B);