Here we ensure that the key student_id is part of the request. Although this validation works, it really does not belong in the function itself. Plus, perhaps there are other routes that use the exact same validation. So, let’s keep it DRY and abstract out any unnecessary logic with a decorator. The following @validate_json decorator will do the job:
Decorator Abstractions: A decorator abstraction is an abstract class that implements the component interface. Critically, the decorator abstraction must also contain a pointer to some instance of the same interface. Inside the decorator abstraction, each of the component interface behaviors will be delegated to whichever concrete component the pointer indicates.
One of the other advantages of the decorator pattern is that wrapped objects can retain the type of the original object. As a result, you can use original and wrapped objects interchangeably, which is a significant advantage when your goal is to write flexible code. In this manner, you can easily extend the behavior of a particular object without modifying the original code.
Just take a look at the code again. In the if/else clause we are returning greet and welcome, not greet() and welcome(). Why is that? It’s because when you put a pair of parentheses after it, the function gets executed; whereas if you don’t put parenthesis after it, then it can be passed around and can be assigned to other variables without executing it. Did you get it? Let me explain it in a little bit more detail. When we write a = hi(), hi() gets executed and because the name is yasoob by default, the function greet is returned. If we change the statement to a = hi(name = "ali") then the welcome function will be returned. We can also do print hi()() which outputs now you are in the greet() function.
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