How data drives the interface.
WHAT THE PROPERTY WRAPPERS DO
Declare how a view relates to a piece of data.
WHAT LOCAL STATE IS FOR
Simple values owned by one view.
WHAT A BINDING IS
A reference to state owned elsewhere, allowing a child to read and write it.
WHAT OBSERVED OBJECTS ARE FOR
Reference types whose changes the view should react to.
WHAT ENVIRONMENT VALUES PROVIDE
Data passed implicitly down the hierarchy, without threading it through every view.
WHEN TO USE THAT
Values many views need: a theme, a session, a formatter.
WHAT THE PRINCIPLE IS
One source of truth for each piece of data.
WHAT VIOLATING IT PRODUCES
Copies that diverge, and interfaces showing inconsistent values.
WHAT TO KEEP LOCAL
Transient interface state.
WHAT TO KEEP IN A MODEL OBJECT
Anything the screen's logic owns.
WHAT TO AVOID
Deriving values and storing them Passing bindings through many levels Heavy work in the view body
WHY THAT LAST POINT
The body may be evaluated frequently.
