"""

*TL;DR

Separates data in GUIs from the ways it is presented, and accepted.

"""

# model，存储数据

# view，基于模型api，写视图

# 控制器，不同模型不同视图

# 模型

class Model:

def __iter__(self):

raise NotImplementedError

def get(self, item):

"""Returns an object with a .items() call method

that iterates over key,value pairs of its information."""

raise NotImplementedError

@property

def item_type(self):

raise NotImplementedError

# 产品模型

class ProductModel(Model):

class Price(float):

"""A polymorphic way to pass a float with a particular

__str__ functionality."""

def __str__(self):

return "{:.2f}".format(self)

products = {

'milk': {'price': Price(1.50), 'quantity': 10},

'eggs': {'price': Price(0.20), 'quantity': 100},

'cheese': {'price': Price(2.00), 'quantity': 10},

}

item_type = 'product'

def __iter__(self):

for item in self.products:

yield item

def get(self, product):

try:

return self.products[product]

except KeyError as e:

raise KeyError(str(e) + " not in the model's item list.")

# 抽象视图

class View:

def show_item_list(self, item_type, item_list):

raise NotImplementedError

def show_item_information(self, item_type, item_name, item_info):

"""Will look for item information by iterating over key,value pairs

yielded by item_info.items()"""

raise NotImplementedError

def item_not_found(self, item_type, item_name):

raise NotImplementedError

# 终端视图

class ConsoleView(View):

def show_item_list(self, item_type, item_list):

print(item_type.upper() + ' LIST:')

for item in item_list:

print(item)

print('')

@staticmethod

def capitalizer(string):

return string[0].upper() + string[1:].lower()

def show_item_information(self, item_type, item_name, item_info):

print(item_type.upper() + ' INFORMATION:')

printout = 'Name: %s' % item_name

for key, value in item_info.items():

printout += ', ' + self.capitalizer(str(key)) + ': ' + str(value)

printout += '\n'

print(printout)

def item_not_found(self, item_type, item_name):

print('That {} "{}" does not exist in the records'.format(item_type, item_name))

# 控制器，有模型和视图

class Controller:

def __init__(self, model, view):

self.model = model

self.view = view

def show_items(self):

items = list(self.model)

item_type = self.model.item_type

self.view.show_item_list(item_type, items)

def show_item_information(self, item_name):

try:

item_info = self.model.get(item_name)

except Exception:

item_type = self.model.item_type

self.view.item_not_found(item_type, item_name)

else:

item_type = self.model.item_type

self.view.show_item_information(item_type, item_name, item_info)

if __name__ == '__main__':

model = ProductModel()

view = ConsoleView()

controller = Controller(model, view)

controller.show_items()

controller.show_item_information('cheese')

controller.show_item_information('eggs')

controller.show_item_information('milk')

controller.show_item_information('arepas')

### OUTPUT ###

# PRODUCT LIST:

# cheese

# eggs

# milk

#

# PRODUCT INFORMATION:

# Name: Cheese, Price: 2.00, Quantity: 10

#

# PRODUCT INFORMATION:

# Name: Eggs, Price: 0.20, Quantity: 100

#

# PRODUCT INFORMATION:

# Name: Milk, Price: 1.50, Quantity: 10

#

# That product "arepas" does not exist in the records