Further information about Factory method Design Pattern about design-patterns-in-ios HOT 3 CLOSED

Hello Alexandre,

I am glad you found the explanation of the design patterns useful and thank you for the positive feedback!

Regarding your question about a positive aspect that I mentioned for the Factory Method that "Supports the Open-Closed Principle by allowing the addition of new subclasses without modifying the existing factory class." I look a it like this:

We know that the Open-Closed principle states that software entities should be open for extension, but closed for modification.

In the example that you provided by creating a new object WhatsApp that conforms to the MessageSender protocol, we need to update the enum MessageType to contain that new case whatsApp.

I see this as an extension of the types that the Factory class can support and not a modification to that class because the return will always be a MessageSender so we are not modifying the end result we are just extending its functionalities to support the creation of new objects.

All the best,

Kevin

from design-patterns-in-ios.

Hello Kevin,
Thank you for your clear answer. I understand much better the O/C principles,

Without modifying the existing factory class. doesn't mean "forbidden to modify the existing factory class". It rather means, not making changes that could lead to modifications for customers who use this factory.

That's right ?

Alexandre

from design-patterns-in-ios.

Hello Alexandre,

You're welcome, I am glad that my explanation helped you to better understand the O/C principles.

Yes, that was my intention when I implemented the Factory Design Pattern in this example so you will be able to extend it but that will not affect the other parts of your code that already use it.

from design-patterns-in-ios.