From: Jim Weirich <jim@...>
Date: 2005-08-12T14:27:32+09:00
Subject: Re: Head First Design Patterns - Strategy Pattern [was: Java/C# "interface" in Ruby ?]

On Thursday 11 August 2005 11:41 pm, dave.burt@gmail.com wrote:
> If a Strategy is a single function, I'd probably do it more like this,
> though:
[... proc based solution elided ...]

Agreed, unless the strategy object requires state.  E.g.

  class Employee
    attr_accessor :payment_strategy
    def pay
      @payment_strategy.pay
    end
  end

  class HourlyStrategy
    def initialize(hourly_rate, timecards)
      @rate = hourly_rate
      @timecards = timecards
    end
    def pay
      @timecards.inject(0.0) { |s, tc| s + tc.calculate_pay(@rate) }
    end
  end

  class SalaryStrategy
    def initialize(salary)
      @weekly_salary = salary
    end
    def pay
      @weekly_salary
    end
  end

-- 
-- Jim Weirich    jim@weirichhouse.org     http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct, 
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)