设计模式Before-after之原型模式

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before.cxx

#include <iostream>class Factorial {public:Factorial(unsigned int n) {double value = 1;for (unsigned int k = 2; k < n; ++k) {value *= k;}this->value = value;}void displayValue(void) {std::cout << this->value << std::endl;}private:double value;};int main(void) {Factorial factorial1(100);factorial1.displayValue();Factorial factorial2(100);factorial2.displayValue();Factorial factorial3(100);factorial3.displayValue();return 0;}

after.cxx

#include <iostream>class Prototype {public:virtual Prototype *clone(void) = 0;};class Factorial: public Prototype {public:Factorial(unsigned int n) {double value = 1;for (unsigned int k = 2; k < n; ++k) {value *= k;}this->value = value;}void displayValue(void) {std::cout << this->value << std::endl;}Prototype *clone(void) {Factorial *copy = reinterpret_cast<Factorial *>(new unsigned char[sizeof Factorial]);*copy = *this;return copy;}private:double value;};int main(void) {Factorial factorial1(100);factorial1.displayValue();Factorial *factorial2 = static_cast<Factorial *>(factorial1.clone());factorial2->displayValue();delete factorial2;Factorial *factorial3 = static_cast<Factorial *>(factorial1.clone());factorial3->displayValue();delete factorial3;return 0;}

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