小さなストッククラブがクラブに関するデータを簡単に管理および表示できるようにする Django アプリを構築しようとしています。私が遭遇した問題は、エレガントで論理的なモデルを構築することです。モデルを構築するための「良い」方法、またはモデルの計画を開始するための「良い」方法についての文献を見つけたことがありません。
それらを論理的に構築していますか？より良い方法はありますか？私はコード自体のスタイル (最終的には PEP-8 に準拠する予定です) には関心がありませんが、設計のロジックとエレガンスには関心があります。
目的が何であるかをよりよく理解するために、モデルに含まれるデータが生成するものの非常にわかりやすい例を次に示します: http://www.bierfeldt.com/takestock/clubs/1/
モデルが現在どのように見えるかのフローチャートの設計は次のとおりです。
ありがとうございました。
models.py
from django.db import models
####### Stock Models #######
class Stock(models.Model):
'''A stock whose current_price is updated every minute by a cronned script
running on the server. The current_price updating script gets all Stock objects
and runs Google Finance queries on each Stock
Stock has no relation to a particular owner, for that, see StockInstance model below'''
ticker = models.CharField(max_length=200)
current_price = models.DecimalField(max_digits=20, decimal_places=2)
def __unicode__(self):
return str(self.ticker + ">" + str(self.current_price))
class StockInstance(models.Model):
'''A middle-man model which links a Stock model to an owner (see Club model below.)
A single owner may possess multiple instances of a single stock purchased at different times
ex. December 9, 2012 - Owner buys 20 shares of AAPL at $500
December 13, 2012 - Owner buys 15 shares of AAPL at $482'''
owner = models.ForeignKey('Club')
stock = models.ForeignKey(Stock)
def current_price(self):
#Current Price of relevant stock
return self.stock.current_price
shares = models.IntegerField()
purchase_date = models.DateTimeField()
purchase_price = models.DecimalField(max_digits=20, decimal_places=2)
#if is_open is False, the instance is considered a closed position
is_open = models.BooleanField(default=True)
sell_date = models.DateTimeField(blank=True, null=True)
sell_price = models.DecimalField(max_digits=20, decimal_places=2, blank=True, null=True)
def current_value(self):
#Current value of this stock instance
#ex. $200 Current Price * 10 shares = $2000
return (self.current_price() * self.shares)
def purchase_value(self):
#Purchase value of this stock instance
#ex. $195 Purchase Price * 10 shares = $1950
return (self.purchase_price * self.shares)
def percent_gl(self):
#Percent Gained/Lost
#ex. ($2000 Current Value - $1950 Purchase Value) / ($1950 Purchase Value) = .03 (03%) Gained
return ((self.current_value() - self.purchase_value()) / (self.purchase_value()))
def amount_gl(self):
#Dollar Value Gained/Lost
#ex. $2000 Current Value - $1950 Purchase Value = $50 Gained
return (self.current_value() - self.purchase_value())
def total_percentage(self):
#Percent of Club Value (all club assets including cash) which this stock instance comprises
#ex. $2000 Current Value / $10000 Club Total Assests = .20 (20%)
return (self.current_value() / self.owner.current_value())
def __unicode__(self):
return str(str(self.shares) + str(" of ")+ str(self.stock.ticker))
####### Member Models #######
class Member(models.Model):
'''Members may belong to multiple clubs. The Member model has no relation to a club
See MemberInstance model below'''
name = models.CharField(max_length=200)
created_at = models.DateTimeField(auto_now_add = True)
updated_at = models.DateTimeField(auto_now = True)
def __unicode__(self):
return self.name
class MemberInstance(models.Model):
'''A middle-man model which links a Member model to an owner (see Club model below.)
A single member may belong to multiple clubs at the same time
ex. John has 5 shares of "Sandstone Investment Club"
John has 15 shares of "Blackwell Investment Firm"'''
owner = models.ForeignKey('Club')
member = models.ForeignKey(Member)
shares = models.DecimalField(max_digits=20, decimal_places=2)
def total_share_value(self):
#Total Dollar value of all of particular member's shares of a club
#ex. Sandstone Investment Club's Share Price is $20 and John has 5 shares
#ex. cont. $20 * 5 shares = $100 value of John's shares in Sandstone Investment Club
return (self.shares * self.owner.current_price())
def total_share_percentage(self):
#Percent of a club that a particular member owns
#ex. John has $100 of Sandstone Investment, Sandstone Investment is worth $1000
#ex. cont. $100 / $1000 = .10 (10%) John owns 10% of Sandstone Investment's Value
return (float(self.total_share_value()) / float(self.owner.current_value()))
####### Club Models #######
class Club(models.Model):
'''A Stock Club
A club has members (MemberInstance) and buys Stocks (StockInstance).
A note on the real-life purpose of stock clubs: Small-tim individual investors often do not have the
buying power to make powerful stock purchases. A single individual may not be able to buy 50 shares
of a stock priced at $500 each. This individual joins a stock club, possibly with friends, family, or co-workers.
The stock club has a number of shares that each member owns some of. The stock CLUB may own shares of many different
STOCKS, but the club only has ONE stock price--its own.'''
name = models.CharField(max_length=200)
created_at = models.DateTimeField(auto_now_add = True)
updated_at = models.DateTimeField(auto_now = True)
cash = models.DecimalField(max_digits=20, decimal_places=2)
def total_shares(self):
#The number of shares of the club that exist
#ex. John has 6 shares of the club; Bob has 4 shares of the club
#ex. cont. The club has (6+4=9) 10 total shares among its members.
shares = 0
for member in self.memberinstance_set.select_related():
shares = shares + member.shares
return shares
def current_value(self):
#The current value of the club
#The current value of each stock instance plus the club's uninvested cash
#ex. $200 from AAPL StockInstance + $400 from GOOG Instance + $20 cash = $620
value = 0
for stock in self.stockinstance_set.select_related():
if stock.is_open == True:
value = value + stock.current_value()
else:
pass
return (self.cash + value)
def current_price(self):
#The club's current share price
#The current value of the club divided by the total number of shares of the club
#ex. $620 Club Current Value / 10 Total Shares = $62 per share
return (self.current_value() / self.total_shares())
def cash_total_percentage(self):
#Percent of club's current value that is uninvested cash
return ((self.cash) / (self.current_value()))
def __unicode__(self):
return self.name