Simplify behavior management with Pattern Strategy in PHP and Symfony

Sometimes you have a piece of code that may behave differently depending on the situation. For example, you may need to calculate a rate differently based on customer type, or apply a specific sorting algorithm. Instead of enclosing these behaviors in big ifs or switches, you can use the Design Pattern Strategy to better structure your code.

Why Pattern Strategy?

The Pattern Strategy allows you to separate the action logic from the rest of the code, so that you can easily change or replace this logic without having to modify your entire program. If you have several ways to perform an action, this is where this pattern becomes very useful. Rather than having a big conditional block, you delegate the behavior to a specific object.

Concrete example: Discount calculation based on customer type

Let's say you're developing an online store and you need to calculate a discount for different types of customers (standard, premium, VIP). Instead of writing conditions for each type of customer everywhere in your code, you will be able to use the Pattern Strategy to encapsulate each reduction calculation in a dedicated class.

Step 1: Policy interface

We will start by creating an interface DiscountStrategy which defines a calculate() method that each discount calculation strategy must implement.

Step 2: Specific Strategies

Next, we will create the different reduction calculation strategies. For example, for standard customers, there is no reduction:

For premium customers, we will apply a 10% reduction:

And for VIP customers, a huge 20% discount:

Step 3: Context Class

Now, we will create a class that will use these strategies. This class does not worry about the type of reduction to apply, it delegates this logic to the strategy given to it.

Step 4: Using in Symfony

Great! We will now see how we can integrate all of this into a Symfony controller. You'll choose a strategy based on the client type, but all the calculation logic remains in the strategy classes, which makes your controller much simpler and cleaner.

What it brings you

1. Flexibility: Thanks to the Pattern Strategy, you can easily add or modify behaviors without touching your main code. All you need to do is add a new calculation strategy.

2. Clean and readable code: Your code becomes much more readable by eliminating massive if or switch blocks. Each policy has its own class with a single responsibility, which follows the Single Responsibility Principle (SRP).

3. Scalability: If one day you need to add a discount for super VIPs with an obscene 50% discount, you simply create a new strategy and the rest of your code doesn't change !

In summary

Pattern Strategy is an excellent choice when you have several ways to execute the same action and you want your code to remain flexible and scalable. Rather than ending up with endless conditions, you encapsulate behaviors in dedicated classes, which allows you to easily interchange them.

And have you already used the Pattern Strategy in your Symfony projects? Don’t hesitate to comment on this article!

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