Why is addField called in the constructor in the code and what problems does it create in terms of scalability?

Calling addField in the constructor often means that fields or properties are added immediately upon object creation, which can lead to tight coupling and reduced flexibility.

Scalability issues:

• Hard to extend: adding new fields requires changing the constructor, violating the open/closed principle.
• Tight coupling: the constructor knows details of the fields, complicating reuse and testing.
• Inheritance problems: if the class is extended, the constructor needs to be overridden to add new fields.
• Configuration difficulties: it is impossible to dynamically change the set of fields without modifying the constructor code.

It is better to use patterns like Builder or factory, where fields are added explicitly and flexibly, or to apply composition and configuration objects for setting up fields after creating an instance.