Don't Call Us, We'll Call You TL;DR: The Hollywood Principle promotes loose coupling by inverting control. High-level components decide when and how to use low-level components. Problems Tight coupling
Difficult to extend
Reduced flexibility
Increased complexity
Violation of SOLID principles
Lack of Testability Solutions Apply Inversion of control


Use Dependency injection


Depend on abstractions Context The Hollywood Principle is a software design principle emphasizing loose coupling between components. High-level components should not directly control the execution flow in low-level components. Low-level components should register themselves with high-level components, and high-level components should decide when and how to use them. This is also known as Inversion of Control. Sample Code Wrong class TicketCart {
    private paymentMethod: PaymentMethod;

    constructor(paymentMethodType: string) {
        // TicketCart is tightly coupled
        // to specific payment method classes 
        // like CreditCardProcessor and CryptoService.  
        if (paymentMethodType === 'creditCard') {
            this.paymentMethod = new CreditCardProcessor();
        } else if (paymentMethodType === 'Crypto') {
            this.paymentMethod = new CryptoService();
        } else {
            throw new Error('Invalid payment method');
        }
    }

    checkout(money: Money): void {
        this.paymentMethod.pay(money);
    }
}

const cart = new TicketCart('creditCard');
const money = new Money(126, 'USD');
cart.checkout(money); Right interface PaymentMethod {
    pay(total: Money): void;
}

class TicketCart {
    private paymentMethod: PaymentMethod;

    constructor(paymentMethod: PaymentMethod) {
        // This solution is more open and less coupled
        // because it relies on abstractions
        this.paymentMethod = paymentMethod;
    }

    checkout(total: Money): void {
        this.paymentMethod.pay(total);
    }
}

class CreditCardProcessor implements PaymentMethod {
    pay(total: Money): void {
        console.log(`Processing payment of ${total.Amount()} 
        ${total.currency()} using credit card.`);
    }
}

const creditCardProcessor = new CreditCardProcessor();
const cart = new TicketCart(creditCardProcessor);
const total = new Money(126, 'USD');
cart.checkout(total); Detection [x]Manual This is a design smell Tags Coupling Level [X ] Intermediate AI Generation AI generators can sometimes create code that violates the Hollywood Principle if you don't explicitly instruct them to follow inversion of control patterns. They often generate straightforward, tightly coupled code by default. AI Detection AI tools can effectively detect violations of the Hollywood Principle by analyzing code dependencies and identifying tight coupling with proper instructions. (see below). Try Them! Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini Conclusion This principle can improve your code quality, reduce complexity, and enhance testability. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxx https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-vii-8dk31x0 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-iv-7sc3w8n https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii More Info https://hackernoon.com/coupling-the-one-and-only-software-designing-problem-9z5a321h?embedable=true https://en.wikipedia.org/wiki/Inversion_of_control?embedable=true https://en.wiktionary.org/wiki/Hollywood_principle?embedable=true Disclaimer Code Smells are my opinion. "Dependency Injection is fundamentally about passing dependencies to objects, rather than having objects create or find them." Martin Fowler https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true This article is part of the CodeSmell Series. How to Find the Stinky Parts of your Code Don't Call Us, We'll Call You Don't Call Us, We'll Call You TL;DR: The Hollywood Principle promotes loose coupling by inverting control. High-level components decide when and how to use low-level components. TL;DR: The Hollywood Principle promotes loose coupling by inverting control. High-level components decide when and how to use low-level components. Problems Tight coupling Difficult to extend Reduced flexibility Increased complexity Violation of SOLID principles Lack of Testability Tight coupling coupling Difficult to extend Reduced flexibility Increased complexity Violation of SOLID principles Lack of Testability Solutions Apply Inversion of control Use Dependency injection Depend on abstractions Apply Inversion of control Apply Inversion of control Use Dependency injection Use Dependency injection Depend on abstractions Depend on abstractions Context The Hollywood Principle is a software design principle emphasizing loose coupling between components. Hollywood Principle High-level components should not directly control the execution flow in low-level components. should not Low-level components should register themselves with high-level components, and high-level components should decide when and how to use them. when how This is also known as Inversion of Control . Inversion of Control Sample Code Wrong class TicketCart {
    private paymentMethod: PaymentMethod;

    constructor(paymentMethodType: string) {
        // TicketCart is tightly coupled
        // to specific payment method classes 
        // like CreditCardProcessor and CryptoService.  
        if (paymentMethodType === 'creditCard') {
            this.paymentMethod = new CreditCardProcessor();
        } else if (paymentMethodType === 'Crypto') {
            this.paymentMethod = new CryptoService();
        } else {
            throw new Error('Invalid payment method');
        }
    }

    checkout(money: Money): void {
        this.paymentMethod.pay(money);
    }
}

const cart = new TicketCart('creditCard');
const money = new Money(126, 'USD');
cart.checkout(money); class TicketCart {
    private paymentMethod: PaymentMethod;

    constructor(paymentMethodType: string) {
        // TicketCart is tightly coupled
        // to specific payment method classes 
        // like CreditCardProcessor and CryptoService.  
        if (paymentMethodType === 'creditCard') {
            this.paymentMethod = new CreditCardProcessor();
        } else if (paymentMethodType === 'Crypto') {
            this.paymentMethod = new CryptoService();
        } else {
            throw new Error('Invalid payment method');
        }
    }

    checkout(money: Money): void {
        this.paymentMethod.pay(money);
    }
}

const cart = new TicketCart('creditCard');
const money = new Money(126, 'USD');
cart.checkout(money); Right interface PaymentMethod {
    pay(total: Money): void;
}

class TicketCart {
    private paymentMethod: PaymentMethod;

    constructor(paymentMethod: PaymentMethod) {
        // This solution is more open and less coupled
        // because it relies on abstractions
        this.paymentMethod = paymentMethod;
    }

    checkout(total: Money): void {
        this.paymentMethod.pay(total);
    }
}

class CreditCardProcessor implements PaymentMethod {
    pay(total: Money): void {
        console.log(`Processing payment of ${total.Amount()} 
        ${total.currency()} using credit card.`);
    }
}

const creditCardProcessor = new CreditCardProcessor();
const cart = new TicketCart(creditCardProcessor);
const total = new Money(126, 'USD');
cart.checkout(total); interface PaymentMethod {
    pay(total: Money): void;
}

class TicketCart {
    private paymentMethod: PaymentMethod;

    constructor(paymentMethod: PaymentMethod) {
        // This solution is more open and less coupled
        // because it relies on abstractions
        this.paymentMethod = paymentMethod;
    }

    checkout(total: Money): void {
        this.paymentMethod.pay(total);
    }
}

class CreditCardProcessor implements PaymentMethod {
    pay(total: Money): void {
        console.log(`Processing payment of ${total.Amount()} 
        ${total.currency()} using credit card.`);
    }
}

const creditCardProcessor = new CreditCardProcessor();
const cart = new TicketCart(creditCardProcessor);
const total = new Money(126, 'USD');
cart.checkout(total); Detection [x]Manual [x] Manual [x] This is a design smell Tags Coupling Coupling Level [X ] Intermediate AI Generation AI generators can sometimes create code that violates the Hollywood Principle if you don't explicitly instruct them to follow inversion of control patterns. inversion of control They often generate straightforward, tightly coupled code by default. AI Detection AI tools can effectively detect violations of the Hollywood Principle by analyzing code dependencies and identifying tight coupling with proper instructions. (see below). Try Them! Remember: AI Assistants make lots of mistakes Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini Without Proper Instructions

With Specific Instructions ChatGPT

ChatGPT Claude

Claude Perplexity

Perplexity Copilot

Copilot Gemini

Gemini Without Proper Instructions With Specific Instructions Without Proper Instructions Without Proper Instructions With Specific Instructions With Specific Instructions ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT Claude Claude Claude Claude Claude Claude Claude Claude Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Copilot Copilot Copilot Copilot Copilot Copilot Copilot Copilot Gemini Gemini Gemini Gemini Gemini Gemini Gemini Gemini Conclusion This principle can improve your code quality, reduce complexity, and enhance testability. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxx https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxx https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-vii-8dk31x0 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-vii-8dk31x0 https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-iv-7sc3w8n https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-iv-7sc3w8n https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii More Info https://hackernoon.com/coupling-the-one-and-only-software-designing-problem-9z5a321h?embedable=true https://hackernoon.com/coupling-the-one-and-only-software-designing-problem-9z5a321h?embedable=true https://en.wikipedia.org/wiki/Inversion_of_control?embedable=true https://en.wikipedia.org/wiki/Inversion_of_control?embedable=true https://en.wiktionary.org/wiki/Hollywood_principle?embedable=true https://en.wiktionary.org/wiki/Hollywood_principle?embedable=true Disclaimer Code Smells are my opinion . opinion "Dependency Injection is fundamentally about passing dependencies to objects, rather than having objects create or find them." "Dependency Injection is fundamentally about passing dependencies to objects, rather than having objects create or find them." Martin Fowler Martin Fowler https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true This article is part of the CodeSmell Series. How to Find the Stinky Parts of your Code How to Find the Stinky Parts of your Code

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