Proxy Pattern blog post

bank.rb

class Bank
 def bank_balance(account_number)
   42
 end
end

bank = Bank.new
p bank.bank_balance("1234567") # ---> Gives me 42

bank2.rb

class LogBankBalanceFilter
 def initialize(bank)
   @bank = bank
 end

 def bank_balance(account_number)
   p "#{account_number} is checking balance"
   balance = @bank.bank_balance(account_number)
   p "the balance was #{balance}"
   return balance
 end
end

bank = LogBankBalanceFilter.new(Bank.new)
p bank.bank_balance("1234567") # --> "123456 is checking balance", "the balance was 42", 42

bank3.rb

class DoubleBankBalanceFilter
 def initialize(bank)
   @bank = bank
 end

 def bank_balance(account_number)
   2 * @bank.bank_balance(account_number)
 end
end

bank = DoubleBankBalanceFilter.new(LogBankBalanceFilter.new(Bank.new))
p bank.bank_balance("1234567") # --> "123456 is checking balance", "the balance was 42", 84

bank4.rb

bank = LogBankBalanceFilter.new(DoubleBankBalanceFilter.new(Bank.new))
p bank.bank_balance("1234567") # --> "123456 is checking balance", "the balance was 84", 84

bank5.rb

class CachingFilter
  def initialize(bank)
    @bank = bank
    @cache = {}
  end

  def bank_balance(account_number)
    if @cache[account_number].nil?
      @cache[account_number] = @bank.bank_balance(account_number)
    end
    @cache[account_number]
  end
end

bank = LogBankBalanceFilter.new(DoubleBankBalanceFilter.new(CachingFilter.new(Bank.new)))
p bank.bank_balance("1234567") # --> "123456 is checking balance", "the balance was 84", 84,. The second call will be cached

dynamicproxy.rb

class Filter
  def initialize(obj)
    @obj = obj
  end

  def method_missing(sym, *args)
    @obj.send(sym, *args)
  end
end

rack.rb

class FooRackMiddleware
  def initialize(app)
    @app = app
  end

  def call(env)
    status, headers, body = @app.call env
    [status, headers, body]
  end
end