Some random sins I’ve encountered while working on code that was written by someone else, in no particular order.

Respect Model/View/Controller.

Specifically views are responsible for their own layout and their own appearance. When controller code (or, God help you, model code) reaches into the innards of a view object in order to start rearranging the contents of the view object, then all sorts of horrors can ensue.

(In the code I just looked at, a UITableViewCell contains two images and three label objects. But the UITableViewCell is not responsible for laying its elements out; instead, the controller code which creates and populates the UITableViewCell is reaching in and moving the contents of the UITableViewCell around.

Why this is bad is because when the height of the view cell is later adjusted because it’s a non-standard height, you cannot simply respond to the layoutSubview method–as all the layout logic is contained in the controller code rather than in the table cell.)

When building complex table views or complex view layouts, consider drawing the view by hand.

On Android and iOS, scrolling a lot of views is expensive. Apple even notes this in their discussions about UITableViewCell. You are almost always better off (assuming your drawing code is fast) drawing the contents of the tableviewcell (or other elements of your user interface) rather than cobbling it together with a bunch of desecrate views.

Sometimes, of course, it’s easier to use a discrete view, and it’s not unreasonable to use a hybrid approach with a single image view added to a custom view which draws the other graphical elements.

On iOS things are a lot easier if you use a tool such as PaintCode, which automatically generates code for you.

Don’t subvert the standard way of doing things.

In the code I’m looking someone built a custom back button which looks almost exactly like iOS 6’s back button.

Guess what? In iOS 7 the back button looks totally different.

And as far as I can tell there was no need to build the custom back button at all.

(They haven’t tested this against iOS 7 yet. I sense pain and frustration.)