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app/models/cash_trade.rb

@@ -6,18 +6,23 @@ class CashTrade < Trade
 	def security
 		Cash.first
 	end
+
 	def vol
 		self.amount
 	end
 	def price
 		1
 	end
 	def cf
-		self.amount
+		- super
 	end
+
 	def is_cash?
 		true
 	end
+	def fee
+		0
+	end
 
 	private
 		def default_values

app/models/portfolio.rb

@@ -22,12 +22,11 @@ def position(*from, till)
 		position = Hash.new { |hash, key| hash[key] = {:position => 0, :cost => 0} }
 		return position	if ts.nil?
 		ts.each { |t| 
-			next if t.is_cash?
 			vol = position[t.security][:position]
 			cost = position[t.security][:cost]
 			position[t.security][:position]= (t.buy ? (vol+t.vol) : (vol-t.vol))
 			if t.buy
-				position[t.security][:cost]=(vol*cost + (t.vol*t.price+t.fee))/(vol+t.vol)
+				position[t.security][:cost]=(vol*cost + (t.amount+t.fee))/(vol+t.vol)
 			end
 		}
 		position

app/models/trade.rb

@@ -7,6 +7,7 @@ class Trade < ActiveRecord::Base
 	belongs_to :portfolio
 	belongs_to :security
 
+	validates :buy, :inclusion => {:in => [true, false]}
 	validates :portfolio_id, :existence => true
 	validates :security_id, :existence => true
 	validates :trade_date, :presence => true
@@ -15,7 +16,7 @@ class Trade < ActiveRecord::Base
 					:unless => Proc.new{|trade| trade.type == "CashTrade"} 
 	validates :price, :numericality => {:greater_than_or_equal_to => 0},
 					:unless => Proc.new{|trade| trade.type == "CashTrade"} 				
-	validates :amount,  :numericality => true
+	validates :amount,  :numericality => {:greater_than_or_equal_to => 0}
 	validate :trade_date_must_be_no_later_than_clear_date
 
 	# Return cashflow for this trade

lib/tasks/sample_data.rake

@@ -47,7 +47,6 @@ namespace :db do
                              :clear_date => tdate,
                              :vol => 100.00,
                              :price => 19.00,
-                             :amount => 100 * 19.00 +1.5,
                              :fee => 1.5,
                              :security_id => @gree.id
                              )
@@ -60,7 +59,6 @@ namespace :db do
                                :clear_date => tdate.next_day(n),
                                :vol => 100.00 * n,
                                :price => 20.00 * (1 + n.to_f/100),
-                               :amount => 100 * n * 20.00 * (1 + n.to_f/100) +1.5 * n,
                                :fee => 1.5 * n,
                                :security_id => @cmb.id
                                )
@@ -73,7 +71,6 @@ namespace :db do
                              :clear_date => tdate.next_day(1),
                              :vol => 100.00,
                              :price => 20.00,
-                             :amount => 100.00 * 20.00 - 1.5,
                              :fee => 1.5,
                              :security_id => @gree.id
                              )
@@ -86,7 +83,6 @@ namespace :db do
                                :clear_date => tdate.next_day(n).advance(:hours => 3),
                                :vol => 100.00 * n,
                                :price => 20.00 * (1 + n.to_f/100),
-                               :amount => 100.00 * n * 20.00 * (1 + n.to_f/100) - 1.5 * n,
                                :fee => 1.5 * n,
                                :security_id => @cmb.id
                                )
@@ -101,7 +97,6 @@ namespace :db do
                               :clear_date => tdate.next_day(n),
                               :vol => 100.00 * n,
                               :price => 25.00 * (1 + n.to_f/100),
-                              :amount => 100.00 * n * 25.00 * (1 + n.to_f/100) + 1.5 * n,
                               :fee => 1.5 * n,
                               :security_id => @cnooc.id
                               )
@@ -116,7 +111,6 @@ namespace :db do
                               :clear_date => tdate.next_day(n).advance(:hours => 3),
                               :vol => 100.00 * n,
                               :price => 25.00 * (1 + n.to_f/100),
-                              :amount => 100 * n * 25.00 *(1 + n.to_f/100) - 1.5 * n,
                               :fee => 1.5 * n,
                               :security_id => @cnooc.id
                               )

spec/factories.rb

@@ -41,6 +41,7 @@
     association :security
   end
   factory :cash_trade do |cash_trade|
+    buy true
     trade_date DateTime.parse("2012-07-19")
     amount 100
     association :portfolio

spec/models/cash_trade_spec.rb

@@ -5,12 +5,14 @@
 	let(:stock) { FactoryGirl.create(:stock) }
 	let(:cash_trade) { FactoryGirl.create(:cash_trade) }
 	let(:trade) { FactoryGirl.create(:trade) }
-
+	subject { cash_trade }
   it "should create a CashTrade even if a security_id hasn't been set" do
     portfolio.cash_trades.create!(
+      :buy => false,
       :trade_date => DateTime.parse("2012-07-19"),
       :amount => 100)
   end
+
   it "should return Cash as Security even if security is set otherwise" do
   	cash_trade.security = Stock.first
   	cash_trade.security.should == Cash.first

spec/models/trade_spec.rb

@@ -131,6 +131,11 @@
       @trade.vol = -1
       @trade.should_not be_valid
     end
+    it "is not valid if price < 0 " do
+      @trade.price = -1
+      @trade.should_not be_valid
+    end
+
   end
 end