How do setNeedsLayout and layoutIfNeeded differ in terms of updating the interface layout?

setNeedsLayout and layoutIfNeeded are UIView methods for managing layout updates.

• setNeedsLayout marks the view as needing a layout update. It is an asynchronous call: the system schedules a call to layoutSubviews in the next interface update cycle.

• layoutIfNeeded forces the view to update its layout immediately if it has been marked as needing an update. If setNeedsLayout was called earlier, then layoutIfNeeded will call layoutSubviews right away.

Example:

view.setNeedsLayout() // mark that an update is needed
// ...
view.layoutIfNeeded() // update immediately if needed

Thus, setNeedsLayout defers the update, and layoutIfNeeded performs it immediately if necessary.