IOS Swift Direction Lock Enabled in ScrollView

In xcode, there is an option for UIScrollViews called Direction Lock Enabled. But the explanation is less than useful – “a boolean value that determines if scrolling is disabled in a particular direction“.

What it really does is disabled multiple direction scrolling. Once you start scrolling in one direction, say horizontally, it will lock the ability to move vertically. Which this sounds awesome, but it has a mode that confuses me — Diagonal.

Modes:

• Horizontal Only
• Vertical Only
• Diagonal Only