Python: Visitor Pattern

GeovinDuVisitor.py

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107

# 访问者模式 Visitor Pattern GeovinDuVistitor.py   class Courses_At_GFG:       def accept(self, visitor):         visitor.visit(self)       def teaching(self, visitor):         print(self, "教授於 ", visitor)       def studying(self, visitor):        print(self, "學習於 ", visitor)       def __str__(self):        return self.__class__.__name__     """Concrete Courses_At_GFG class: Classes being visited."""     class SDE(Courses_At_GFG): pass     class STL(Courses_At_GFG): pass     class DSA(Courses_At_GFG): pass     """ Abstract Visitor class for Concrete Visitor classes:  method defined in this class will be inherited by all  Concrete Visitor classes."""     class Visitor:     def __str__(self):         return self.__class__.__name__     class Instructor(Visitor):     def visit(self, crop):         crop.teaching(self)     class Student(Visitor):     def visit(self, crop):         crop.studying(self)   # 二類 class Item():     """Visitable class"""     def accept(self):         pass   class Shirt(Item):     def __init__(self, price, size):         self.price = price         self.size = size       def get_price(self):         return self.price       def get_size(self):         return self.size       def accept(self, visitor):         return visitor.visit(self)   class Book(Item):     def __init__(self, cost, genre):         self.price = cost         self.genre = genre       def get_price(self):         return self.price       def get_genre(self):         return self.genre       def accept(self, visitor):         return visitor.visit(self)   class Visitor():     """Abstract Vistor Class"""       def visit(self, item):         pass   class CartVisitor(Visitor):     def visit(self, item):         if isinstance(item, Book):             cost = item.get_price()             print("书的类型: {}, 费用 = ${}".format(item.get_genre(), cost))             return cost         elif isinstance(item, Shirt):             cost = item.get_price()             print("衬衫,尺寸{} 费用 = ${}".format(item.get_size(), cost))             return cost   def calculate_price(items):     visitor = CartVisitor()     sum = 0     for item in items:         sum = sum + item.accept(visitor)       return sum

　　

main.py 调用

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

# 访问者模式 Visitor Pattern sde = GeovinDuVisitor.SDE() stl = GeovinDuVisitor.STL() dsa = GeovinDuVisitor.DSA()   """Creating Visitors""" instructor = GeovinDuVisitor.Instructor() student = GeovinDuVisitor.Student()   """Visitors visiting courses""" sde.accept(instructor) sde.accept(student)   stl.accept(instructor) stl.accept(student)   dsa.accept(instructor) dsa.accept(student)   items = [         GeovinDuVisitor.Shirt(10, "XL"),         GeovinDuVisitor.Shirt(15, "XXL"),         GeovinDuVisitor.Book(20, "虚构小说"),         GeovinDuVisitor.Book(100, "自助"),     ]   total = GeovinDuVisitor.calculate_price(items) print("涂聚文所购总成本 = ${}".format(total))

　　

输出：

?

1 2 3 4 5 6 7 8 9 10 11

SDE 教授於  Instructor SDE 學習於  Student STL 教授於  Instructor STL 學習於  Student DSA 教授於  Instructor DSA 學習於  Student 衬衫,尺寸XL 费用 = $10 衬衫,尺寸XXL 费用 = $15 书的类型: 虚构小说, 费用 = $20 书的类型: 自助, 费用 = $100 涂聚文所购总成本 = $145