[C++知识库]c++ CRTP静多态的实现(vs 动多态)

#include <iostream>
using namespace std;

// 动多态
class VirObj {
 public:
    virtual void what() const {
        cout << "Obj !!!" << endl;
    }
};

class VirAnimal : public VirObj {
 public:
    void what() const override {
        cout << "Animal !!!" << endl;
    }
};

// CRTP 静多态
template<typename T>
class Base {
 public:
    void what() const {
        ((T *)this)->sayWhat();
    }
};

class BaseAnimal : public Base<BaseAnimal> {
 public:
    void sayWhat() const { //NOLINT
        cout << "BaseAnimal !!!" << endl;
    }
};

// 动多态的使用方式
template<typename T>
void virtualWhat(const T &t) {
    t.what();
}

// 静多态的使用方式, 注意观察二者的差别
template<typename T>
void noVirtualWhat(const Base<T> &t) {
    t.what();
}

int main() {
    BaseAnimal ba;
    noVirtualWhat(ba);

    VirObj *vo = new VirAnimal;
    virtualWhat(*vo);
}