重构：Query Method

重构：使用查询函数替换临时变量

最新推荐文章于 2024-07-18 19:18:28 发布

NickAsuo

最新推荐文章于 2024-07-18 19:18:28 发布

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分类专栏：重构文章标签：重构

本文链接：https://blog.youkuaiyun.com/qq_21381465/article/details/51298722

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本文讨论了在重构代码时如何用查询函数替代临时变量，以提高代码的可读性和可维护性。通过实例展示了如何将总费用和频繁租赁积分从临时变量转换为查询方法，从而简化代码逻辑。

在重构：Replace Temp with Query中，用查询函数（query method）来取代totalAmount 和frequentRentalPoints这两个临时变量。首先用getTotalCharge()取代totalAmount:

public class Customer {
    private String _name;
    private Vector<Rental> _rentals = new Vector<Rental>();;

    public Customer(String name) {
        _name = name;
    }

    public void addRental(Rental arg) {
        _rentals.addElement(arg);
    }

    public String getName() {
        return _name;
    }

    public String statement() {

        int frequentRenterPoints = 0;
        Enumeration<Rental> rentals = _rentals.elements();
        String result = "Rental Record For " + getName() + "\n";
        while (rentals.hasMoreElements()) {

            Rental each = (Rental) rentals.nextElement();


            frequentRenterPoints += each.getFrequentRenterPoints();

            result += "\t" + each.getMovie().getTitle() + "\t" + String.valueOf(each.getCharge()) + "\n";

        }
        result += "Amount owed is " + String.valueOf(getTotalCharge()) + "\n";
        result += "You earned " + String.valueOf(frequentRenterPoints) + " frequent renter points";
        return result;
    }
    private double getTotalCharge() {
        double result = 0;
        Enumeration<Rental> rentals = _rentals.elements();
        while (rentals.hasMoreElements()) {
            Rental each = (Rental) rentals.nextElement();
            result += each.getCharge();
        }
        return result;
    }

}

用getTotalFrequentRenterPoints（）取代frequentRenterPoints:

public class Customer {
    private String _name;
    private Vector<Rental> _rentals = new Vector<Rental>();;

    public Customer(String name) {
        _name = name;
    }

    public void addRental(Rental arg) {
        _rentals.addElement(arg);
    }

    public String getName() {
        return _name;
    }

    public String statement() {
        Enumeration<Rental> rentals = _rentals.elements();
        String result = "Rental Record For " + getName() + "\n";
        while (rentals.hasMoreElements()) {

            Rental each = (Rental) rentals.nextElement();
            result += "\t" + each.getMovie().getTitle() + "\t" + String.valueOf(each.getCharge()) + "\n";

        }
        result += "Amount owed is " + String.valueOf(getTotalCharge()) + "\n";
        result += "You earned " + String.valueOf(getTotalFrequentRenterPoints()) + " frequent renter points";
        return result;
    }
    private double getTotalCharge() {
        double result = 0;
        Enumeration<Rental> rentals = _rentals.elements();
        while (rentals.hasMoreElements()) {
            Rental each = (Rental) rentals.nextElement();
            result += each.getCharge();
        }
        return result;
    }
    private int getTotalFrequentRenterPoints() {
        int result = 0;
        Enumeration<Rental> rentals = _rentals.elements();
        while (rentals.hasMoreElements()) {
            Rental each = (Rental) rentals.nextElement();
            result += each.getFrequentRenterPoints();
        }
        return result;
    }
}