C ++中的Dynamic_cast和static_cast
static_cast：用于普通/普通类型转换。这也是负责隐式类型强制的强制转换，也可以显式调用。在将float转换为int，将char转换为int等情况下，应使用它。这可以转换相关的类型类。如果类型不同，则会产生一些错误。
示例
#include<iostream>
using namespace std;
class Base {};
class Derived : public Base {};
class MyClass {};
main(){
Derived* d = new Derived;
Base* b = static_cast<Base*>(d); // this line will work properly
MyClass* x = static_cast<MyClass*>(d); // ERROR will be generated during compilation
}输出结果
[Error] invalid static_cast from type 'Derived*' to type 'MyClass*'
dynamic_cast：此强制转换用于处理多态。您只需要在转换为派生类时使用它。从基类转换为派生类时，只能在继承中使用它。
示例
#include<iostream>
using namespace std;
class MyClass1 {
public:
virtual void print()const {
cout << "This is from MyClass1\n";
}
};
class MyClass2 {
public:
virtual void print()const {
cout << "This is from MyClass2\n";
}
};
class MyClass3: public MyClass1, public MyClass2 {
public:
void print()const {
cout << "This is from MyClass3\n";
}
};
int main(){
MyClass1* a = new MyClass1;
MyClass2* b = new MyClass2;
MyClass3* c = new MyClass3;
a -> print();
b -> print();
c -> print();
b = dynamic_cast< MyClass2*>(a); //This cast will be failed
if (b)
b->print();
else
cout << "no MyClass2\n";
a = c;
a -> print(); //Printing from MyClass3
b = dynamic_cast< MyClass2*>(a); //Successfully casting is done
if (b)
b -> print();
else
cout << "no MyClass2\n";
}输出结果
This is from MyClass1 This is from MyClass2 This is from MyClass3 no MyClass2 This is from MyClass3 This is from MyClass3
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