重构14-Break Responsibilities

把一个类的多个职责进行拆分，这贯彻了SOLID中的单一职责原则（SRP）。尽管对于如何划分“职责”经常存在争论，但应用这项重构还是十分简单的。我这里并不会回答划分职责的问题，只是演示一个结构清晰的示例，将类划分为多个负责具体职责的类。

public class Video {
    public void PayFee(Double fee) {
    }
    public void RentVideo(Video video, Customer customer) {
        customer.Videos.add(video);
}
    public Double CalculateBalance(Customer customer) {
        return customer.sum(customer.LateFees);
}
}
public class Customer {
    public List<Double> LateFees;
    public List<Video> Videos;
    double sum(List<Double> LateFees){
        double sum=0d;
        for (Double d:LateFees){
            sum=+d;
}
        return sum;
}
}

如你所见，Video类包含两个职责，一个负责处理录像租赁，另一个负责管理管理用户的租赁总数。要分离

职责，我们可以将用户的逻辑转移到用户类中。 

public class Video {
    public void RentVideo(Video video, Customer customer) {
        customer.Videos.add(video);
}
}

public class Customer {
    public List<Double> LateFees;
    public List<Video> Videos;
    public void PayFee(Double fee){}
    public Double CalculateBalance(Customer customer) {
        return sum(customer.LateFees);
}
    double sum(List<Double> LateFees) {
        double sum = 0d;
        for (Double d : LateFees) {
            sum = +d;
}
        return sum;
}
}

来自为知笔记(Wiz)