Design-pattern -Strategy--and--Factory--Adapter

Design-pattern -Strategy--and--Factory--Adapter.rb

class CreditCardPayment
  def pay(amount)
    puts "Processing credit card payment of #{amount}"
  end
end

class PayPalPayment
  def pay(amount)
    puts "Processing PayPal payment of #{amount}"
  end
end

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# Define Strategies, For Behaviour Design Pattern

class PaymentProcessor
  def initialize(strategy)
    @strategy = strategy
  end

  def process_payment(amount)
    @strategy.pay(amount)
  end
end

# Use different strategies at runtime
payment = PaymentProcessor.new(CreditCardPayment.new)
payment.process_payment(100)

payment = PaymentProcessor.new(PayPalPayment.new)
payment.process_payment(200)

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###  Factory design Pattern under Creational Design Pattern 

class PaymentFactory
  def self.create(payment_method)
    case payment_method
    when :credit_card
      CreditCardPayment.new
    when :paypal
      PayPalPayment.new
    else
      raise "Unknown payment method: #{payment_method}"
    end
  end
end

# Use the factory to create instances
payment = PaymentFactory.create(:credit_card)
payment.pay(100)

payment = PaymentFactory.create(:paypal)
payment.pay(200)


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### Adapter pattern For Structural Design Pattern


# Existing incompatible APIs
class StripeAPI
  def charge(amount)
    "Charged $#{amount} using Stripe"
  end
end

class PayPalAPI
  def make_payment(amount)
    "Paid $#{amount} using PayPal"
  end
end

# Adapter
class PaymentAdapter
  def initialize(payment_system)
    @payment_system = payment_system
  end

  def pay(amount)
    if @payment_system.is_a?(StripeAPI)
      @payment_system.charge(amount)
    elsif @payment_system.is_a?(PayPalAPI)
      @payment_system.make_payment(amount)
    else
      raise "Unsupported payment system"
    end
  end
end

# Usage
stripe_payment = PaymentAdapter.new(StripeAPI.new)
puts stripe_payment.pay(100)  # Output: "Charged $100 using Stripe"

paypal_payment = PaymentAdapter.new(PayPalAPI.new)
puts paypal_payment.pay(200)  # Output: "Paid $200 using PayPal"