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Code without decorator design pattern

To exemplify, we have a Pizza factory that has a plain pizza (basically the dough) and then you can choose the ingredients.

To achieve that, we created 3 classes:

  • Pizza Carbonara
  • Pizza Pepperoni
  • Pizza Extra Cheese

Each class have the ingredients statically defined, to this example we used a string (description) to register the ingredients but in a real app/system we could have a list of ingredients saved in the database or other platform. But what it's important to understand is that each class has the ingredients statically defined, so, if a pizza changes an ingredient or if a factory would like to change an existing pizza, the code must be changed, compiled and deployed in order for that to take effect in the next orders.

In the class Program.cs, we are creating this 3 types of pizzas:

var pizzaCarbonara = new PizzaCarbonara();
pizzaCarbonara.Print();

var pizzaPepperoni = new PizzaPepperoni();
pizzaPepperoni.Print();

var pizzaExtraCheese = new PizzaExtraCheese();
pizzaExtraCheese.Print();

And the output is the following:

Creating pizza Carbonara
Ingredients: Crisp pieces of salt bacon, mushrooms, gooey cheese and egg
Cost: 10.5

Creating pizza Pepperoni
Ingredients: Salami, paprika, garlic, black pepper, red pepper, cayenne pepper, mustard seed and fennel seed
Cost: 11.5

Creating pizza with extra Cheese
Ingredients: Mozzarella, parmesan, fontina, cheddar, provolone, pecorino romano and ricotta
Cost: 11

We can see for the code and structure that each time this pizza factory wants to create a new pizza, needs to create e new class and define the ingredients.

If the price of the tomato sauce, for example, changes, all the GetCost() method from all classes of pizzas that has tomato sauce needs to be changed.

Also, if a customer wants to create a custom pizza, the developers needs to find a way to make that possible with the code as is in this example.

We will see this same scenario but using Decorator pattern - all this "problems" are solved with it

Try it yourself

You can run the console application to see the output in the console.

To do that, you can use your IDE buttons/options or via terminal, executing the following command:

before executing the command, cd to this repository root directory

dotnet run --project ./DecoratorPattern/DecoratorPattern.WithoutPattern/DecoratorPattern.WithoutPattern.csproj

Now lets see the code using the decorator pattern 👇

📄 Code using decorator pattern