Clean redundant code

app/models/concerns/base_transaction.rb

@@ -0,0 +1,31 @@
+module BaseTransaction
+  extend ActiveSupport::Concern
+  include ActionView::Helpers::NumberHelper
+
+  included do
+    belongs_to :debtor,   class_name: 'User'
+    belongs_to :creditor, class_name: 'User'
+    belongs_to :issuer,   polymorphic: true
+
+    validates :amount, numericality: { greater_than: 0 }
+    validate :different_debtor_creditor
+  end
+
+  def info
+    attributes.symbolize_keys.extract!(
+      :debtor_id, :creditor_id, :issuer_id, :issuer_type, :message, :amount
+    )
+  end
+
+  def amount_f
+    number_to_currency amount/100.0, unit: '€'
+  end
+
+  private
+
+  def different_debtor_creditor
+    if self.debtor == self.creditor
+      self.errors.add :base, "Can't write money to yourself"
+    end
+  end
+end

app/models/concerns/transaction_helpers.rb

@@ -0,0 +1,12 @@
+module TransactionHelpers
+  include ActiveSupport::Concern
+
+  def peer_of(user)
+    return creditor if user == debtor
+    return debtor   if user == creditor
+  end
+
+  def is_client_transaction?
+    issuer_type == 'Client'
+  end
+end

app/models/request.rb

@@ -1,21 +1,13 @@
 class Request < ActiveRecord::Base
-  belongs_to :debtor,   class_name: 'User'
-  belongs_to :creditor, class_name: 'User'
-  belongs_to :issuer,   polymorphic: true
-
-  validates :amount, numericality: { greater_than: 0 }
-  validate  :different_debtor_creditor
+  include BaseTransaction
 
   enum status: [:open, :confirmed, :declined]
 
   def confirm!
     return unless open?
 
-    Transaction.create attributes.symbolize_keys.extract!(
-      :debtor_id, :creditor_id, :issuer_id, :issuer_type, :amount, :message
-    )
-
-    creditor.notifications.create message: "Your request for €#{amount/100.0} for \"#{message}\" has been accepted by #{debtor.name}."
+    Transaction.create info
+    Notification.create user: creditor,message: confirmed_message
 
     update_attributes status: :confirmed
   end
@@ -23,15 +15,18 @@ class Request < ActiveRecord::Base
   def decline!
     return unless open?
 
-    creditor.notifications.create message: "#{debtor.name} refuses to pay €#{amount/100.0} for \"#{message}\"."
+    Notification.create user: creditor, message: declined_message
+
     update_attributes status: :declined
   end
 
   private
 
-  def different_debtor_creditor
-    if self.debtor == self.creditor
-      self.errors.add :base, "Can't write money to yourself"
+  def confirmed_message
+    "Your request for €#{amount/100.0} for \"#{message}\" has been accepted by #{debtor.name}."
   end
+
+  def declined_message
+    "#{debtor.name} refuses to pay €#{amount/100.0} for \"#{message}\"."
   end
 end

app/models/transaction.rb

@@ -15,22 +15,13 @@
 #
 
 class Transaction < ActiveRecord::Base
-  belongs_to :debtor, class_name: 'User'
-  belongs_to :creditor, class_name: 'User'
-  belongs_to :issuer, polymorphic: true
+  include BaseTransaction
+  include TransactionHelpers
 
-  after_save    :recalculate_balances
-  after_destroy :recalculate_balances
+  after_save    :recalculate_balances!
+  after_destroy :recalculate_balances!
 
-  validates :amount, numericality: { greater_than: 0 }
   validates :id_at_client, presence: true, uniqueness: { scope: :issuer_id }, if: :is_client_transaction?
-  validate :different_debtor_creditor
-
-
-  def peer_of(user)
-    return creditor if user == debtor
-    return debtor if user == creditor
-  end
 
   def signed_amount_for(user)
     return -amount if user == debtor
@@ -42,24 +33,10 @@ class Transaction < ActiveRecord::Base
     self.amount *= -1
   end
 
-  def info
-    attributes.symbolize_keys.extract!(:debtor_id, :creditor_id, :issuer_id, :issuer_type, :message, :amount)
-  end
-
   private
 
-  def recalculate_balances
+  def recalculate_balances!
     creditor.calculate_balance!
     debtor.calculate_balance!
   end
-
-  def different_debtor_creditor
-    if self.debtor == self.creditor
-      self.errors.add :base, "Can't write money to yourself"
-    end
-  end
-
-  def is_client_transaction?
-    issuer_type == "Client"
-  end
 end

app/views/requests/_index.html.haml

@@ -14,7 +14,7 @@
       %tr
         %td= r.creditor.name
         %td= r.issuer.name
-        %td= "€#{r.amount/100.0}"
+        %td= r.amount_f
         %td= r.message
         - if actions
           %td