ryanlintott

In XCode 16.2 beta 3 the onPreferenceChange view modifier closure was changed to be @Sendable. This change caused a number of errors in my code when I try to use the value in the closure to update a view property.

I’ve attached a simple WidthReader example that shows these errors.

This change seems similar to the recent change to the alignmentGuide closure. The difference is the alignmentGuide closure is used to change the value of the alignment guide and I have no expectation of using it to update view properties. The onPreferenceChange closure returns no value and as far as I can figure the only use of it would be to modify view properties.

As a workaround I could wrap each modification in a main actor Task but I’m concerned about this somehow delaying my updates and causing visual glitches in the UI.

Ideally I would like the onPreferenceChange modifier to be annotated with @MainActor instead of @Sendable as I can’t see a use case when someone would use the value to update something off the main thread.

ryanlintott

struct CrashingView: View {
    @State private var items: [String] = Array(1...10).map { String("\($0)") }
    
    var body: some View {
        VStack {
            HStack {
                ForEach(items, id: \.self) { item in
                    Text(item)
                        /// Adding @Sendable to the closure fixes the crash
                        .alignmentGuide(HorizontalAlignment.center) { @Sendable d in

ryanlintott

import SwiftData

extension ModelContext {
    /// FetchDescriptor is Sendable but inside a parameter pack there are sometimes issues with this working in Swift 6.0
    func fetch<each T: PersistentModel, Result: Sendable>(
        _ descriptor: repeat FetchDescriptor<each T>,
        with closure: @escaping @Sendable (repeat [each T]) throws -> Result
    ) throws -> Result {
        try closure(repeat try fetch(each descriptor))
    }

ryanlintott

//
//  CrashingView.swift
//  CrashRemovingItem
//
//  Created by Ryan Lintott on 2024-08-13.
//

import SwiftUI

struct CrashingView: View {

ryanlintott

//
//  CrashingView.swift
//  CrashRemovingItem
//
//  Created by Ryan Lintott on 2024-08-13.
//

import SwiftUI

fileprivate struct _VariadicRoot: _VariadicView_MultiViewRoot {

ryanlintott

//
//  NoClipTextRenderer.swift
//  
//
//  Created by Ryan Lintott on 2024-07-08.
//

import SwiftUI

@available(iOS 18, *)

ryanlintott

//
//  AutoLayoutTestApp.swift
//  AutoLayoutTest
//
//  Created by Ryan Lintott on 2024-03-07.
//

import FrameUp
import SwiftUI

ryanlintott

//
//  ShrinkingLabel.swift
//  FrameUpExample
//
//  Created by Ryan Lintott on 2024-02-21.
//

import FrameUp
import SwiftUI

ryanlintott

//
//  KeyboardButtonStyle.swift
//  Wordhord
//
//  Created by Ryan Lintott on 2024-02-06.
//

import ShapeUp
import SwiftUI

ryanlintott

import SwiftUI

struct Theme: Identifiable {
    let id: UUID
    let name: String
}

extension Theme {
    static let blue = Self(id: UUID(), name: "Blue")
    static let red = Self(id: UUID(), name: "Red")