Main page: Attribute Graph.

In this article, I say node but in the Attribute Graph this is typically called an attribute .

The Attribute Graph in SwiftUI builds up a graph of the SwiftUI views we declare. It creates nodes for the views, the view’s’ inputs and the view’s outputs. The graph is mostly static. While properties change a lot, nodes mostly stay persistent and don’t get recreated all the time.

• For each SwiftUI view, a body node will be part of the graph, containing the entire view body

• A State property in a view gets turned into its own node. Every view body that reads the state property creates a (dynamic) dependency on that node.

Views are compared for equality to see if they are marked as dirty (and need to reevaluate their body). See view equality in SwiftUI.

Environment

As the Attribute Graph builds up, SwiftUI keeps track of the current environment node. If a view reads from the environment a dependency is created. If a view modifies the environment, the modified environment points to the previous node, and the subtree will receive the modified environment node. You can see this in my presentation at 9:39.

Preferences

I’m not quite sure yet how to implement this, TBD.