Updating attributes through a different object - ruby-on-rails

Question

I am having a ridiculously hard time trying to figure out how to do this. I have been at it literally all day.
I have an Account class and a Transaction class.
Accounts are created with a balance and I want the Transaction amount, depending on its type, to either add or subtract from the balance.
I want to be able to update the Account balance every time a transaction is created. This is for a personal finance application. As of now when I create a new transaction, nothing happens to the account balance.
accounts_controller.rb
class AccountsController < ApplicationController
def index
#accounts = Account.all
end
def show
#account = Account.find(params[:id])
end
def new
#account = Account.new
end
def edit
#account = Account.find(params[:id])
end
def create
#account = Account.new(params[:account])
respond_to do |format|
if #account.save
format.html { redirect_to #account, notice: 'Account was successfully created.' }
format.json { render json: #account, status: :created, location: #account }
else
format.html { render action: "new" }
format.json { render json: #account.errors, status: :unprocessable_entity }
end
end
end
def update
#account = Account.find(params[:id])
respond_to do |format|
if #account.update_attributes(params[:account])
format.html { redirect_to #account, notice: 'Account was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: "edit" }
format.json { render json: #account.errors, status: :unprocessable_entity }
end
end
end
# DELETE /accounts/1
# DELETE /accounts/1.json
def destroy
#account = Account.find(params[:id])
#account.destroy
respond_to do |format|
format.html { redirect_to accounts_url }
format.json { head :no_content }
end
end
def update_balance
#a = Account.find(params[:id])
#a.transactions.each do |t|
#update_balance = t.t_type + #a.balance
#a.update_attributes(:balance => #update_balance)
end
end
end
transactions_controller.rb
class TransactionsController < ApplicationController
def create
#account = Account.find(params[:account_id])
#transaction = #account.transactions.create(params[:transaction])
redirect_to account_path(#account)
end
end
transaction.rb
class Transaction < ActiveRecord::Base
belongs_to :account
attr_accessible :amount, :category, :t_type
end
account.rb
class Account < ActiveRecord::Base
attr_accessible :balance, :name
has_many :transactions
end
If anyone has any idea what I'm doing wrong or can point me in the direction of a good thorough explanation, that would be great. I am so lost at this point.

Answer 1

Try this.
class Account < ActiveRecord::Base
attr_accessible :balance, :name
has_many :transactions
def update_with_transaction(transaction)
return unless self.transactions.include? transaction
if transaction.t_type.eql? SOME_TYPE
self.balance += transaction.ammount
else
self.balance -= transaction.ammount
end
save
end
end
class TransactionsController < ApplicationController
def create
account = Account.find(params[:account_id])
#transaction = account.transactions.create(params[:transaction])
account.update_with_transaction(#transaction)
redirect_to account_path(account)
end
end

Answer 2

It doesn’t update because you haven’t told it to. Create an after_create callback to do so:
class Transaction < ActiveRecord::Base
# ...
after_create :update_account_balance
private
def update_account_balance
account.balance += amount
account.save
end
end
Adjust as needed. Note that this won’t handle updates to a transaction’s amount, which is left as an exercise for the reader.