Property wrappers

In Swift, property wrappers are program entities with names starting with @.

Property wrappers are “logic” code fragments, which are executed whenever set or get is executed on that property. In our case, a property or an attribute is, to keep things simple, just a fancy name for a variable within our struct.

So, whenever you “do” something to that variable, the corresponding property wrapper will be invoked.

In the case of @State, which is a property wrapper defined by Apple, it tells the following SwiftUI a few things about the view struct:

• It tells SwiftUI that the value should be persisted and not reset to its initial value whenever the view gets redrawn
• It tells SwiftUI that a property’s value is allowed to change
• It tells SwiftUI to redraw that corresponding view whenever the @State property changes

The following figure shows you a conceptual flowchart on how SwiftUI uses the @State wrapper to...