Module 1: The Ultimate Goal: The Perfect Pizzeria
Imagine you’re building your own pizzeria. You want it to be so well designed that if you decide to change the wall color (the user interface) or replace your fridge (the database), your chef never has to change the recipe for your signature pizza.
That’s what Clean Architecture is all about: making sure the secret recipes (your most important code) are protected and don’t depend on anything other than solid ideas.
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Module 2: The Magic Circles (The Layers)
Architecture is drawn with concentric circles, like Russian nesting dolls.
The Center (The Core): This is where your recipes and rules live (the Domain). It’s the most precious and least changeable part.
Around It (The Chefs): These are the people who apply the recipes (the Use Cases).
Further Out (The Translators): These are the servers that translate the customer’s order into chef language (the Adapters).
The Outside (The Details): This is the real world: the customers’ tables (the UI) and the fridge (the Database).
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Module 3: The Core: The Secret Recipes (Entities)
At the center, we have the Entities. Think of them as the Original Recipe Book of your pizzeria.
Role: They contain the basic rules, like: "A pizza must always have tomato and cheese," or "The minimum price for a drink is €2."
Protection: They know NOTHING about the website’s color or the type of fridge used. They are pure and stable.
Our Motto: These are the rules that never change, even if the application does.
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Module 4: The Head Chef (Use Cases)
Right after the Recipe Book, there’s the Head Chef. These are the Use Cases.
Role: Their job is to take a specific order ("Make a Margherita") and follow the steps: get the ingredients from storage, follow the Entity recipe, and give the pizza to the server.
Application Logic: This is the Chef’s logic, not the recipe itself. For example: "If the order is placed after 10 PM, add a €1 night surcharge."
Order: Use Cases are the only ones allowed to modify the Entities.
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Module 5: The Golden Rule: Never Look Outside
This is the most important and magical rule of Clean Architecture:
Dependencies can only point inward.
The Chef (Inside) cannot depend on the Server (Outside). The Chef doesn’t care if the Server is wearing jeans or a suit. If the Server changes uniform, the Chef doesn’t have to redo the recipe.
The Core never depends on the Outside. If the fridge (DB) breaks, the Recipe Book (Entities) is still fine. This rule isolates the good idea (the Domain) from the technology that keeps changing.
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Module 6: The Servers and Adapters (Interface Adapters)
This layer does the translation work.
The Controller (Server): It receives the customer’s order (a click on the "Order" button). It takes the raw information and transforms it into the exact format that the Chef (Use Case) understands.
The Presenter (Server that brings the plate): Once the pizza is ready, the Chef gives it to the Presenter. The Presenter puts it on a nice plate and makes sure it’s cut into six slices so the customer is happy (preparing it for the UI View).
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Module 7: The Outside World (Frameworks and Details)
This is the layer farthest from the center, the most changeable, and the least precious.
The Dining Room (UI): This is what the customer sees: chairs, tables, colors. Today it’s a website; tomorrow, maybe a mobile app. The Chef doesn’t care.
The Fridge/Storage (Database): This is where the ingredients (data) are stored. Whether you use a Samsung or LG fridge (SQL or NoSQL), the Chef just needs the tomatoes brought to them.
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Module 8: The Secret Service Trick (Dependency Inversion - DIP)
How does the Chef request ingredients without knowing which fridge is being used? It’s magic!
The Chef (Inside): He says, "I need an Ingredient Manager (this is an Interface, a promise)."
The Fridge (Outside): There’s someone called the "LG Fridge Manager," and this person fulfills the role of "Ingredient Manager."
Injection: Someone (in the outermost layer) gives the Chef the phone number of the "LG Fridge Manager" saying, "Here’s your Ingredient Manager!"
Result: The Chef calls the role (the Interface) and not the fridge brand (the concrete implementation). The dependency flow is reversed, and the Core remains pure!
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Module 9: The Storage Boxes (Component Architecture)
Imagine your Chef. He organizes his tools. He doesn’t mix pizza knives with soup ladles.
Key Principle (CCP): Group together things that change for the same reason. If I change the rule about cheese, I put the cheese recipe and the cheese inventory in the same "code box."
Isolation: If you change the "home delivery" box, it shouldn’t affect the "dessert recipes" box. This makes updates faster and safer.
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Module 10: The 5 Developer Commandments (SOLID)
Clean Architecture is just the application of 5 basic rules (called SOLID) to the whole pizzeria:
1.SRP (Single Responsibility Principle): Each person has only one job. The Server doesn’t make pizzas.
2.OCP (Open/Closed Principle): You should be able to add a new recipe (Open) without touching the old ones (Closed).
3.LSP (Liskov Substitution Principle): If you replace your Chef with another Chef of the same title, they must make the same pizzas without breaking the rules.
4.ISP (Interface Segregation Principle): The Chef doesn’t need to know the dishwasher’s rules; they only have their small order notebook. (Small notebooks = small Interfaces)
5.DIP (Dependency Inversion Principle): Our Secret Service trick (Module 8). The Core depends on abstractions, not details.
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