Lecture 9 of Stanford’s iOS Development course from Spring 2020 covers the basics of data flow, including Publishers and Bindings. These mechanisms allow for formalized references to the “truth” of data rather than requiring it to be replicated which can be error-prone. A basic explanation of property wrappers helps clarify what @ObservedObject, @EnvironmentObject, @Published, @State, @Binding, etc. are all about. The demo shows publishing the arrival of the background image for our EmojiArt document as well as auto-saving the document when changes are noticed (i.e. published). Finally, our UI is enhanced to let us choose from multiple palettes of emoji where a Binding is used to link our new palette chooser to our main EmojiArt UI.