Question

I’m trying to create a generic, reusable view, that looks like a lined notepad. The way I decided to approach the problem (after a couple design iterations) is to create a custom view that is composed of a UITextView and a UIView.

When the user scrolls through lines of text I want the UIView to track the scroll direction. The key here is: Within my custom view, I need to change the position of one subview in response to events in another subview. Something needs to coordinate these changes…

Now, one approach I thought of taking was to use a MVC design pattern. A view controller could handle all events and move the subviews around accordingly. This MVC could then be embedded in other MVCs.

Normally when using a MVC design pattern, a controller would handle user events and manipulate the model and view. However, my custom view doesn’t have a model – all I’m trying to do is have the view manage it’s own subviews when a user does something like scroll. It seems to me that the MVC design pattern isn’t a good fit here for two reasons:

1. There isn’t a model or logic that is specific to the program it’s being used in.
2. It seems to me that the view should be responsible for handling user events that change how the view should appear.

… but I could be wrong, which is why I’m asking for help. The question, for those who are more experienced than I and who may have done this many times before, is:

What type of design pattern is appropriate in this situation? MVC or…

Answer 1

You want a view to manage its own subviews? Then do that! So what if that pattern doesn’t have a TLA?

A typical approach is to implement layoutSubviews in your container view. Have it check its current state, or the state of the other views in the window (e.g. the contentOffset of a scroll view), and then set up its subviews appropriately. (Resize them, reposition them, etc.)

Just try to keep it fast, since it’s likely that layoutSubviews will be called frequently.