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Sergey Leschev
Sergey Leschev

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🐝 Chain Of Responsibility

Chain Of Responsibility

The chain of responsibility pattern is used to process varied requests, each of which may be dealt with by a different handler.

Github https://github.com/sergeyleschev/design-patterns

Example:

protocol Withdrawing {
    func withdraw(amount: Int) -> Bool
}

final class MoneyPile: Withdrawing {
    let value: Int
    var quantity: Int
    var next: Withdrawing?

    init(value: Int, quantity: Int, next: Withdrawing?) {
        self.value = value
        self.quantity = quantity
        self.next = next
    }

    func withdraw(amount: Int) -> Bool {
        var amount = amount

        func canTakeSomeBill(want: Int) -> Bool {
            return (want / self.value) > 0
        }

        var quantity = self.quantity

        while canTakeSomeBill(want: amount) {

            if quantity == 0 {
                break
            }

            amount -= self.value
            quantity -= 1
        }

        guard amount > 0 else {
            return true
        }

        if let next = self.next {
            return next.withdraw(amount: amount)
        }

        return false
    }
}

final class ATM: Withdrawing {

    private var hundred: Withdrawing
    private var fifty: Withdrawing
    private var twenty: Withdrawing
    private var ten: Withdrawing

    private var startPile: Withdrawing {
        return self.hundred
    }

    init(hundred: Withdrawing,
           fifty: Withdrawing,
          twenty: Withdrawing,
             ten: Withdrawing) {

        self.hundred = hundred
        self.fifty = fifty
        self.twenty = twenty
        self.ten = ten
    }

    func withdraw(amount: Int) -> Bool {
        return startPile.withdraw(amount: amount)
    }
}
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Usage

// Create piles of money and link them together 10 < 20 < 50 < 100.**
let ten = MoneyPile(value: 10, quantity: 6, next: nil)
let twenty = MoneyPile(value: 20, quantity: 2, next: ten)
let fifty = MoneyPile(value: 50, quantity: 2, next: twenty)
let hundred = MoneyPile(value: 100, quantity: 1, next: fifty)

// Build ATM.
var atm = ATM(hundred: hundred, fifty: fifty, twenty: twenty, ten: ten)
atm.withdraw(amount: 310) // Cannot because ATM has only 300
atm.withdraw(amount: 100) // Can withdraw - 1x100
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Sources: Github

Behavioral
In software engineering, behavioral design patterns are design patterns that identify common communication patterns between objects and realize these patterns. By doing so, these patterns increase flexibility in carrying out this communication.
Source: wikipedia.org


🐝 Chain Of Responsibility
πŸ‘« Command Pattern
🎢 Interpreter Pattern
🍫 Iterator Pattern
πŸ’ Mediator Pattern
πŸ’Ύ Memento Pattern
πŸ‘“ Observer Pattern
πŸ‰ State Pattern
πŸ’‘ Strategy Pattern
πŸ“ Template Method
πŸƒ Visitor Pattern
🌰 Abstract Factory
πŸ‘· Builder Pattern
🏭 Factory Method
πŸ”‚ Monostate Pattern
πŸƒ Prototype Pattern
πŸ’ Singleton
πŸ”Œ Adapter Pattern
πŸŒ‰ Bridge Pattern
🌿 Composite Pattern
🍧 Decorator Pattern
🎁 Facade Pattern
πŸƒ Flyweight Pattern
β˜” Protection Proxy
🍬 Virtual Proxy


Contacts
I have a clear focus on time-to-market and don't prioritize technical debt. And I took part in the Pre-Sale/RFX activity as a System Architect, assessment efforts for Mobile (iOS-Swift, Android-Kotlin), Frontend (React-TypeScript) and Backend (NodeJS-.NET-PHP-Kafka-SQL-NoSQL). And I also formed the work of Pre-Sale as a CTO from Opportunity to Proposal via knowledge transfer to Successful Delivery.

πŸ›©οΈ #startups #management #cto #swift #typescript #database
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πŸ–¨οΈ PDF Design Patterns: Download

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