《重构--改善既有代码的设计》读书笔记之四：将条件分支语句放入合适类中

来源：互联网发布：yaml 数组编辑：程序博客网时间：2024/06/06 07:34

要点：最好不要在另一个对象的属性基础上运用条件分支语句，如果不得不使用，也应该在对象自己的数据上使用。

方法：getCharge() 和 getFrequentRenterPoints()移动到Movie类中去。

在运用继承重构代码之前 rental & movie 代码如下：

rental.h:

#ifndef RENTAL_H#define RENTAL_H#include "movie.h"class Rental{public:Rental(Movie movie, int daysRented);double getCharge();int getDaysRented();Movie getMovie();int getFrequentRenterPoints();private:Movie _movie;int _daysRented;};#endif //RENTAL_H

rental.cpp:

#include "rental.h"Rental::Rental(Movie movie, int daysRented){_movie = movie;_daysRented = daysRented;}double Rental::getCharge(){return _movie.getCharge(_daysRented);}int Rental::getDaysRented(){return _daysRented;}Movie Rental::getMovie(){return _movie;}int Rental::getFrequentRenterPoints() {return _movie.getFrequentRenterPoints(_daysRented);}

movie.h:

#ifndef MOVIE_H#define MOVIE_H#include <string>using std::string;class Movie{public:Movie(string title = "empty", int priceCode = 0);double getCharge(int daysRented);int getFrequentRenterPoints(int daysRented);int getPriceCode();void setPriceCode(int arg);string getTitle();public:static const int REGULAR;static const int NEW_RELEASE;static const int CHILDRENS;private:string _title;int _priceCode;};#endif //MOVIE_H

movie.cpp:

#include "movie.h"const int Movie::REGULAR = 0;const int Movie::NEW_RELEASE = 1;const int Movie::CHILDRENS = 2;Movie::Movie(string title , int priceCode){_title = title;_priceCode = priceCode;}double Movie::getCharge(int daysRented){double result = 0;// determine amounts for each lineswitch(getPriceCode()){case REGULAR:result += 2;if (daysRented > 2){result += (daysRented - 2) * 1.5;}break;case NEW_RELEASE:result += daysRented * 3;break;case CHILDRENS:result += 1.5;if (daysRented > 3){result += (daysRented - 3) * 1.5;}break;}return result;}int Movie::getFrequentRenterPoints(int daysRented) {// add bonus for a two day new release rentalif ((getPriceCode() == NEW_RELEASE) && daysRented > 1)return 2;elsereturn 1;}int Movie::getPriceCode(){return _priceCode;}void Movie::setPriceCode(int arg){_priceCode = arg;}string Movie::getTitle(){return _title;}