Understanding when SwiftUI re-renders an @Observable

jflan · February 15, 2025, 2:11pm

Checking if equatable values changed was added to the set accessor after the release of 6.0. Hopefully it’ll be in 6.1.

github.com/swiftlang/swift

lib/Macros/Sources/ObservationMacros/ObservableMacro.swift

afb4d1397


      
            """
            get {
              access(keyPath: \\.\(identifier))
              return _\(identifier)
            }
            """
          
          let setAccessor: AccessorDeclSyntax =
            """
            set {
              guard shouldNotifyObservers(_\(identifier), newValue) else {
                return
              }
              withMutation(keyPath: \\.\(identifier)) {
                _\(identifier) = newValue
              }
            }
            """
            
          // Note: this accessor cannot test the equality since it would incur
          // additional CoW's on structural types. Most mutations in-place do