MVC vs MVVM: A Real-Life iOS Interview Insight

During a recent interview for an iOS developer position, I came across an interesting question that tested my knowledge of design patterns and my understanding of how they evolve. The discussion revolves around MVC and MVVM, two basic design patterns in iOS development. As I prepared to explain their basics, the interviewer surprised me with a follow-up question.

In this post, I will share the question, my initial response, and what I learned from the experience. If you’re preparing for an iOS interview, this might help you in a similar situation!

Question: “How do controllers fit into MVVM?”

The interview began with a familiar question:
“Can you explain the difference between MVC and MVVM?”

I answered confidently:

• multidimensional controller represent Model-View-Controllerwhere the controller handles user input and updates the view and model accordingly.
• MVVM represent model-view-viewmodelwhere the business logic is separated from the View and placed in the ViewModel.

I was satisfied with my answer, but I didn’t expect the next question to be:
“In MVVM, there is no “controller.” So, where does the role of the controller go?

I was stumped. I hadn’t thought deeply about this difference before. After the interview, I took some time to better reflect and understand the concept.

Learn about MVC and MVVM:

MVC (Model-View-Controller):

• this Model Represents data and business logic.
• this view Display the data to the user.
• this controller Acts as a bridge between the model and the view, processing user input and updating data.

In this model, the controller often takes on a lot of responsibilities, which makes it easy to become “a lot” (The notorious Massive view controllers question).

MVVM (Model-View-ViewModel):

• this Model remain unchanged.
• this view Still dealing with the UI.
• this view model A layer is introduced that manages business logic and data binding to views.

exist MVVMno clear controller. Instead, its responsibilities are spread across view(processing user input) and view model (Handling logic and data).

The role of the controller in MVVM:

exist MVVM based on UIKit In the application, the ViewController still exists, but purely as part of the view. it:

• Handles UI settings and user input.
• Bind the UI to the ViewModel.
• Transfer operations to ViewModel.

exist Swift user interfaceView is directly bound to ViewModel, no separate ViewController is needed at all.

What I gained:

1. The evolution of design patterns:
   It’s important to understand not only the structure, but also the responsibilities of each component.

2. Be prepared for deeper questions:
   Interviewers will often go beyond surface questions to test your understanding of concepts.

3. Reflection is key:
   While I didn’t have a perfect answer at the time, reflecting on this question helped solidify my understanding for the future.

If you’re preparing for an iOS interview, take some time to learn more about how design patterns distribute responsibilities. MVC and MVVM are more than just acronyms – they represent different philosophies for organizing code.

I hope these insights are helpful on your interview journey. Have you ever encountered similar problems? I’d love to hear about your experiences!