What is the Strategy Pattern and Why Is It So Important in Code Review?

In modern software development, code readability and maintainability are among the most critical factors for project success. The Strategy Pattern, as one of the GoF (Gang of Four) design patterns, is a powerful tool that facilitates switching between algorithms and solves the common problem of if-else chains frequently encountered during code review processes.

Today's AI Code Review tools are quite successful at detecting the Strategy Pattern. Using the Strategy Pattern in your code allows you to achieve higher quality scores in automated code review systems.

The Basic Structure of the Strategy Pattern

The Strategy Pattern is a behavioral design pattern that enables algorithm selection at runtime. This pattern is particularly recommended when:

• You need to choose between multiple algorithms.
• If-else or switch-case blocks become complex.
• "Open/Closed Principle" violations are detected in code review.

Implementing the Strategy Pattern

Traditional Approach (A Red Flag in Code Review)

    class PaymentProcessor
      def process_payment(amount, method)
        case method
        when 'credit_card'
          # Credit card transaction
          puts "Processing #{amount} TL with credit card..."
          validate_credit_card
          charge_credit_card(amount)
        when 'paypal'
          # PayPal transaction
          puts "Processing #{amount} TL with PayPal..."
          validate_paypal_account
          charge_paypal(amount)
        when 'bank_transfer'
          # Bank transfer
          puts "Processing #{amount} TL with bank transfer..."
          validate_bank_account
          process_bank_transfer(amount)
        else
          raise "Unsupported payment method: #{method}"
        end
      end
    end

Refactored with Strategy Pattern (Code Review Approved)

    # Strategy Interface
    class PaymentStrategy
      def process(amount)
        raise NotImplementedError, "Subclasses must implement the process method"
      end
    end

    # Concrete Strategies
    class CreditCardStrategy < PaymentStrategy
      def initialize(card_number, cvv)
        @card_number = card_number
        @cvv = cvv
      end

      def process(amount)
        puts "Processing #{amount} TL with credit card..."
        validate_card
        charge_card(amount)
      end

      private

      def validate_card
        # Card validation logic
        puts "Validating card information..."
      end

      def charge_card(amount)
        # Card charging logic
        puts "Charged #{amount} TL from the card"
      end
    end

    class PayPalStrategy < PaymentStrategy
      def initialize(email)
        @email = email
      end

      def process(amount)
        puts "Processing #{amount} TL with PayPal..."
        validate_paypal_account
        charge_paypal(amount)
      end

      private

      def validate_paypal_account
        puts "Validating PayPal account: #{@email}"
      end

      def charge_paypal(amount)
        puts "Charged #{amount} TL from PayPal"
      end
    end

    class BankTransferStrategy < PaymentStrategy
      def initialize(iban)
        @iban = iban
      end

      def process(amount)
        puts "Processing #{amount} TL with bank transfer..."
        validate_iban
        process_transfer(amount)
      end

      private

      def validate_iban
        puts "Validating IBAN: #{@iban}"
      end

      def process_transfer(amount)
        puts "Sent #{amount} TL via bank transfer"
      end
    end

    # Context Class
    class PaymentProcessor
      def initialize(strategy)
        @strategy = strategy
      end

      def change_strategy(strategy)
        @strategy = strategy
      end

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

Usage Example

    # Using different payment strategies
    credit_card = CreditCardStrategy.new("1234-5678-9012-3456", "123")
    paypal = PayPalStrategy.new("user@email.com")
    bank_transfer = BankTransferStrategy.new("TR33 0006 1005 1978 6457 8413 26")

    processor = PaymentProcessor.new(credit_card)
    processor.process_payment(100.0)

    # Changing the strategy
    processor.change_strategy(paypal)
    processor.process_payment(250.0)

    processor.change_strategy(bank_transfer)
    processor.process_payment(500.0)

Advantages of the Strategy Pattern in Code Review

1. Single Responsibility Principle (SRP)

Each strategy class is responsible for only one payment method. This is immediately noticeable in a code review.

2. Open/Closed Principle (OCP)

You don't need to modify existing code to add new payment methods.

    class CryptoStrategy < PaymentStrategy
      def initialize(wallet_address)
        @wallet_address = wallet_address
      end

      def process(amount)
        puts "Processing #{amount} TL with cryptocurrency..."
        validate_wallet
        transfer_crypto(amount)
      end

      # ... other methods
    end

3. Testability

Each strategy can be tested separately, which increases your unit test coverage.

    require 'rspec'

    RSpec.describe CreditCardStrategy do
      let(:strategy) { CreditCardStrategy.new("1234-5678-9012-3456", "123") }

      describe '#process' do
        it 'processes credit card payment successfully' do
          expect { strategy.process(100.0) }.to output(/Processing 100.0 TL with credit card/).to_stdout
        end
      end
    end

AI Code Review Tools and the Strategy Pattern

Modern AI code review tools like Erbab.dev evaluate the use of the Strategy Pattern positively because:

• Cyclomatic Complexity decreases
• Code Duplication is reduced
• Maintainability Index increases
• Technical Debt is lowered

Performance Considerations

Performance points to consider when using the Strategy Pattern:

    class OptimizedPaymentProcessor
      def initialize
        @strategies = {
          'credit_card' => -> { CreditCardStrategy.new },
          'paypal' => -> { PayPalStrategy.new },
          'bank_transfer' => -> { BankTransferStrategy.new }
        }
      end

      def process_payment(amount, method, **options)
        strategy_factory = @strategies[method]
        raise "Unsupported payment method: #{method}" unless strategy_factory

        strategy = strategy_factory.call
        strategy.process(amount)
      end
    end

Real-World Scenarios

Consider using the Strategy Pattern in these situations:

1. E-commerce Platforms: Different payment gateways
2. Logger Systems: Different log formats (JSON, XML, Plain Text)
3. Data Export: Different file formats (CSV, Excel, PDF)
4. Sorting Algorithms: QuickSort, MergeSort, BubbleSort
5. Authentication: OAuth, LDAP, Database

Conclusion

The Strategy Pattern is the most elegant solution for the complex if-else structures frequently encountered in code review processes.

The fact that AI code review tools also favor this pattern shows how important it is in modern software development. This approach, which aligns with clean code and SOLID principles, will also accelerate your team's internal code review processes.

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