From Sicily to Software: SOLID Lessons from The Godfather

I believe that analogy is a powerful approach for understanding complex or abstract concepts. By relating unfamiliar ideas to real-world examples, we can simplify them and make them more engaging. This is why, in this article, I’ve chosen to explain the SOLID principles using The Godfather movie.

As we know, the word SOLID is an acronym that stands for five essential principles of object-oriented software design. Each letter represents a different concept, but together they create a strong foundation for building robust and maintainable systems. What’s even more fascinating is that the structure, roles, and values found in The Godfather align perfectly with these principles. By drawing parallels between Vito Corleone’s leadership and the key concepts of SOLID, we can gain a deeper understanding of both the theory behind software design and the power of effective organizational structure.

As I mentioned on title, I tried to explain SOLID principles with The Godfather movie.

1) Single Responsibility Principle (SRP)

“Don’t ever take sides against the family again.”
— The Godfather by Mario Puzo

Definition: Each class or module should have only one reason to change, focusing on a single responsibility.

Godfather Analogy: In the Corleone family, each member has a specific role:

• Tom Hagen (Consigliere): Provides legal and strategic advice.
• Clemenza and Tessio (Caporegimes): Manage street-level operations and execute orders.
• Sonny and Michael: Handle leadership or specific family disputes.

This structure ensures that each member focuses on their own responsibilities, avoiding overlap or inefficiency. Similarly, in software, separating responsibilities makes the system easier to manage and extend.

class Don{
    leadFamily(): void {
        console.log("Leading the family...");
    }

    makeHimAnOfferHeCantRefuse():void{
        console.log("I'm gonna make him an offer he can't refuse!")
    }
}

class Consigliere {
    provideAdvice(): void {
        console.log("Strategic advice is provided.");
    }
}

class Caporegime {
    executeOrders(): void {
        console.log("Carrying out orders in the field.");
    }
}

Each class focuses on its own mission. Tom Hagen doesn’t do the work on the field; Clemenza doesn’t strategize.

2) Open/Closed Principle (OCP)

“The strength of a family, like the strength of an army, lies in its loyalty to each other.”
— The Godfather by Mario Puzo

Definition: Classes should be open for extension but closed for modification.

Godfather Analogy: When Vito Corleone steps down, Michael Corleone takes over without altering the foundational structure of the family. Michael implements new strategies while keeping the core values and hierarchy intact. Similarly, in software, extending functionality without modifying existing code ensures stability and scalability.

class Don {
    leadFamily(): void {
        console.log("Leading the family...");
    }
}

class MichaelCorleone extends Don {
    leadFamily(): void {
        console.log("Leading with a new strategy.");
    }
}

function startLeadership(don: Don) {
    don.leadFamily();
}

const vito = new Don();
const michael = new MichaelCorleone();

startLeadership(vito);
startLeadership(michael);

Don Vito hands over the leadership role to Michael. The new leadership style is expanded without changing the existing system. Although Michael’s methods are different, the leadership process continues uninterrupted.

3) Liskov Substitution Principle (LSP)

“Never tell anybody outside the family what you’re thinking again.”
— The Godfather by Mario Puzo

Definition: Objects of a superclass should be replaceable with objects of a subclass without altering the correctness of the program.

Godfather Analogy: Michael steps into the role of Don seamlessly after Vito retires. The family continues to function as before because the leadership structure and decision-making process are consistent. In software, subclasses should replace their parent classes without breaking the system’s behavior.

class FamilyMember {
    actOnBehalf(): void {
        console.log("Acting on behalf of the family.");
    }
}

class Don extends FamilyMember {
    actOnBehalf(): void {
        console.log("Leading and making high-level decisions.");
    }
}

class Caporegime extends FamilyMember {
    actOnBehalf(): void {
        console.log("Executing orders in the field.");
    }
}

function representFamily(member: FamilyMember) {
    member.actOnBehalf();
}

const vito = new Don();
const clemenza = new Caporegime();

representFamily(vito);
representFamily(clemenza);

Don Vito or Clemenza act in different roles on behalf of the family, each serving the general function of “representing the family” but doing so in their own way.

4) Interface Segregation Principle (ISP)

“I’m gonna make him an offer he can’t refuse.”
— The Godfather by Mario Puzo

Definition: Clients should not be forced to depend on methods they do not use.

Godfather Analogy: Each role in the family has distinct responsibilities:

• Vito Corleone manages the family and ensures that every member of the family and his associates only handle tasks specific to their expertise, avoiding unnecessary overlap or confusion
• Tom Hagen deals only with legal and political issues.
• Clemenza and Tessio focus on tactical operations.
• Michael Corleone is initially outside the family business but later takes on leadership when strategically necessary.
• Soldiers handle specific tasks like enforcement or protection.

Nobody is overloaded with unrelated responsibilities, ensuring efficiency. Similarly, in software, designing focused interfaces prevents unnecessary dependencies and promotes modularity.

interface Strategic {
    provideAdvice(): void;
}

interface Operational {
    executeOrders(): void;
}

class Consigliere implements Strategic {
    provideAdvice(): void {
        console.log("Providing strategic advice.");
    }
}

class Caporegime implements Operational {
    executeOrders(): void {
        console.log("Executing orders in the field.");
    }
}

Each class gets only the features it needs.

5) Dependency Inversion Principle (DIP)

“It’s not personal, Sonny. It’s strictly business.”
— The Godfather by Mario Puzo

Definition: High-level modules should not depend on low-level modules. Both should depend on abstractions.

Godfather Analogy: The Don Vito Corleone(high-level module) sets the overall vision and strategy but doesn’t micromanage operations. Instead, he relies on caporegimes and soldiers (low-level modules) to execute plans based on abstract directives like “protect the family” or “expand operations.” In software, this principle ensures that high-level policies remain independent of lower-level implementation details, creating a flexible and maintainable system.

interface Leadership {
    lead(): void;
}

class DonVito implements Leadership {
    lead(): void {
        console.log("Leading the family with traditional methods.");
    }
}

class DonMichael implements Leadership {
    lead(): void {
        console.log("Leading the family with new strategies.");
    }
}

class Family {
    private leader: Leadership;

    constructor(leader: Leadership) {
        this.leader = leader;
    }

    operate(): void {
        this.leader.lead();
    }
}

const vito = new DonVito();
const michael = new DonMichael();

const corleoneFamily = new Family(vito);
corleoneFamily.operate();

const modernFamily = new Family(michael);
modernFamily.operate();

The family organization (Family class) is not dependent on the concrete details of the leaders (DonVito or DonMichael). No matter which leader is there, the family can continue to function. This provides independence between strategy and operations.

Conclusion: The Family Code of SOLID Principles

Much like the Corleone family, software systems thrive when built on structure, clarity, and resilience. The SOLID principles mirror the careful organization and delegation seen in The Godfather: responsibilities are clearly defined, adaptability is encouraged without compromising stability, and roles operate independently yet harmoniously under a guiding abstraction.

From Vito’s strategic leadership (DIP) to the focused tasks of his consiglieres and caporegimes (SRP and ISP), the Corleone family’s success was rooted in its ability to balance order and flexibility — qualities that are equally vital in creating robust, maintainable software systems.

By applying the lessons of SOLID principles to your software design, you can build systems that are as enduring and effective as the Corleone legacy: prepared for challenges, resilient to change, and capable of growth. As Vito Corleone himself might say, “Build your system on principles, and it will make you an offer you can’t refuse.”

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