I am a new commer, trying to create Webview with Xcode 12.0.1. I make the code identical to other comments and videos as below but I don't know why the error message "Type 'SwiftUIWebView' does not conform to protocol 'UIViewRepresentable'. Do you want to add protocol stubs?"
import SwiftUI
import WebKit
struct SwiftUIWebView: UIViewRepresentable {
let url: URL?
func makeUIView(Context: Context) -> WKWebView {
let prefs = WKWebpagePreferences()
prefs.allowsContentJavaScript=true
let config = WKWebViewConfiguration()
config.defaultWebpagePreferences = prefs
return WKWebView(
frame: .zero,
configuration: config
)
}
func updateIUView(_ uiView: WKWebView, context: Context) {
guard let myURL = url else {
return
}
let request = URLRequest(url: myURL)
uiView.load( request )
}
}
Can you point out where is the problem and how to solve this?
I want to dynamically deliver content and display hyperlinks, but it can’t be delivered dynamically and doesn’t work
let linkTitle = "Apple Link"
let linkURL = "http://www.apple.com"
let string = "[Apple Link](http://www.apple.com)"
Text(string) // Not working
Text("[Apple Link](http://www.apple.com)") // Working
Text("[\(linkTitle)](http://www.apple.com)") // Working
Text("[\(linkTitle)](\(linkURL))") // Not working
Short Answer
Wrap the string in AttributedString(markdown: my_string_here):
let string: String = "[Apple Link](http://www.apple.com)"
Text(try! AttributedString(markdown: string))
Extension
extension String {
func toMarkdown() -> AttributedString {
do {
return try AttributedString(markdown: self)
} catch {
print("Error parsing Markdown for string \(self): \(error)")
return AttributedString(self)
}
}
}
Long Answer
SwiftUI Text has multiple initializers.
For String:
init<S>(_ content: S) where S : StringProtocol
For AttributedString:
init(_ attributedContent: AttributedString)
When you declare a static string, Swift is able to guess whether the intent is to use a String or AttributedString (Markdown). However, when you use a dynamic string, Swift needs help in figuring out your intent.
As a result, with a dynamic string, you have to explicitly convert your String into an AttributedString:
try! AttributedString(markdown: string)
you can try this taken from: How to show HTML or Markdown in a SwiftUI Text? halfway down the page.
extension String {
func markdownToAttributed() -> AttributedString {
do {
return try AttributedString(markdown: self) /// convert to AttributedString
} catch {
return AttributedString("Error parsing markdown: \(error)")
}
}
}
struct ContentView: View {
let linkTitle = "Apple Link"
let linkURL = "https://www.apple.com"
let string = "[Apple Link](https://www.apple.com)"
#State var textWithMarkdown = "[Apple Link](https://www.apple.com)"
var body: some View {
VStack {
Text(textWithMarkdown.markdownToAttributed()) // <-- this works
Text(string) // Not working
Text("[Apple Link](http://www.apple.com)") // Working
Text("[\(linkTitle)](http://www.apple.com)") // Working
Text("[\(linkTitle)](\(linkURL))") // Not working
}
}
}
Add another .init in text.
struct ContentView: View {
let linkTitle = "Apple Link"
let linkURL = "http://www.apple.com"
let string = "[Apple Link](http://www.apple.com)"
var body: some View {
Text(.init(string)) // <== Here!
Text("[Apple Link](http://www.apple.com)") // Working
Text("[\(linkTitle)](http://www.apple.com)") // Working
Text(.init("[\(linkTitle)](\(linkURL))")) // <== Here!
}
}
Preview canvas is is crashing but in simulator everything working fine. I assuming it related to #ObservedObject and #Fetchrequest...
tried solution for here Previewing ContentView with CoreData
doesn't work
import SwiftUI
import CoreData
struct TemplateEditor: View {
#Environment(\.managedObjectContext) var managedObjectContext
#FetchRequest(
entity: GlobalPlaceholders.entity(),
sortDescriptors: [
NSSortDescriptor(keyPath: \GlobalPlaceholders.category, ascending: false),
]
) var placeholders: FetchedResults<GlobalPlaceholders>
#ObservedObject var documentTemplate: Templates
#State private var documentTemplateDraft = DocumentTemplateDraft()
#Binding var editing: Bool
var body: some View {
VStack(){
HStack(){
cancelButton
Spacer()
saveButton
}.padding()
addButton
ForEach(placeholders) {placeholder in
Text(placeholder.name)
}
TextField("Title", text: $documentTemplateDraft.title)
TextField("Body", text: $documentTemplateDraft.body)
.padding()
.frame(width: 100, height:400)
Spacer()
}
...
}
struct TemplateEditor_Previews: PreviewProvider {
static var previews: some View {
let managedObjectContext = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
let request = NSFetchRequest<NSFetchRequestResult>(entityName: "Templates")
request.sortDescriptors = [NSSortDescriptor(keyPath: \Templates.created, ascending: false)]
let documentTemplate = try! managedObjectContext.fetch(request).first as! Templates
return TemplateEditor(documentTemplate: documentTemplate, editing: .constant(true)).environment(\.managedObjectContext, managedObjectContext).environmentObject(documentTemplate)
}
}
Expected to generate preview
I'm not sure if your try line will work if there is no data.
let documentTemplate = try! managedObjectContext.fetch(request).first as! Templates
To get mine to work I created a test Item to use. Like this:
struct DetailView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
//Test data
let newEvent = Event.init(context: context)
newEvent.timestamp = Date()
return DetailView(event: newEvent).environment(\.managedObjectContext, context)
}
}
I've also noticed that I needed the .environment(.managedObjectContext, context) code in an earlier tabView that hosted the CoreData views or the preview would fail.
This answer seems to work in my recent project by replacing the default ContentView_Previews struct, though others are questioning whether it pulls persistent data. Credit goes to #ShadowDES - in the Master/Detail template project in Xcode Beta 7
I'm able to CRUD anything using Canvas (XCode Version 11.3 (11C29)) and it seems to run flawlessly.
#if DEBUG
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainer.viewContext
return ContentView().environment(\.managedObjectContext, context)
}
}
#endif
What works for me:
I create all of my sample data in the preview property of my persistence controller, building off of the template generated by Xcode when starting a project with the following settings: Interface - SwiftUI, Lifecycle - SwiftUI App, Use Core Data, Host in CloudKit. I have posted the template here:
import CoreData
struct PersistenceController {
static let shared = PersistenceController()
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
let viewContext = result.container.viewContext
// ** Prepare all sample data for previews here ** //
for _ in 0..<10 {
let newItem = Item(context: viewContext)
newItem.timestamp = Date()
}
do {
try viewContext.save()
} catch {
// handle error for production
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
return result
}()
let container: NSPersistentCloudKitContainer
init(inMemory: Bool = false) {
container = NSPersistentCloudKitContainer(name: "SwiftUISwiftAppCoreDataCloudKit")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// handle error for production
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
}
}
In my preview, I inject the persistence controller into the preview environment and for my view argument I use the registeredObjects.first(where:) method on the preview viewContext to pull the first object of the desired type:
struct MyView_Previews: PreviewProvider {
static var previews: some View {
MyView(item: PersistenceController.preview.container.viewContext.registeredObjects.first(where: { $0 is Item }) as! Item)
.environment(\.managedObjectContext, PersistenceController.preview.container.viewContext)
}
}
Edited 11/15/21
Persistence
import CoreData
struct PersistenceController {
static let shared = PersistenceController()
static var preview: PersistenceController = {
let result = PersistenceController(inMemory: true)
let viewContext = result.container.viewContext
Seed().prepareData(for: viewContext)
return result
}()
let container: NSPersistentCloudKitContainer
init(inMemory: Bool = false) {
container = NSPersistentCloudKitContainer(name: "SwiftUISwiftAppCoreDataCloudKit")
if inMemory {
container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
}
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
// handle error for production
fatalError("Unresolved error \(error), \(error.userInfo)")
}
})
}
}
struct Seed {
func prepareData(for viewContext: NSManagedObjectContext) {
// ** Prepare all sample data for previews here ** //
for _ in 0..<10 {
let newItem = Item(context: viewContext)
newItem.timestamp = Date()
}
do {
try viewContext.save()
} catch {
// handle error for production
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
}
}
Item Preview
struct ItemView_Previews: PreviewProvider {
static let persistence = PersistenceController.preview
static var item: Item = {
let context = persistence.container.viewContext
let item = Item(context: context)
item.timestamp = Date()
return item
}()
static var previews: some View {
ItemView(item: item)
.environment(\.managedObjectContext, persistence.container.viewContext)
}
}
So, if you put some code in an onAppear handler in the preview, it will run on boot. It even live updates as you type!
struct TemplateEditor_Previews: PreviewProvider {
static var previews: some View {
TemplateEditor().environment(\.managedObjectContext, AppDelegate.viewContext).onAppear {
let entity = GlobalPlaceholders(context: AppDelegate.viewContext)
entity.name = "abc123"
// Or create more, if you need more example data
try! AppDelegate.viewContext.save()
}
}
}
Note that I've wrapped up my viewContext in a static method on AppDelegate to make access a tiny bit less verbose and easier to remember:
#UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
static var persistentContainer: NSPersistentContainer {
return (UIApplication.shared.delegate as! AppDelegate).persistentContainer
}
static var viewContext: NSManagedObjectContext {
return persistentContainer.viewContext
}
Works for SwiftUI 2 app using the App template
I also had the previews crash and none of the other solutions were suitable or worked for me.
What I did was rather than the following:
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
return ContentView()
.environment(
\.managedObjectContext,
CoreDataManager.context
)
}
}
I fixed it with:
struct ContentView_Previews: PreviewProvider {
static var previews: some View {
let context = CoreDataManager.context
/* Optional sample data can be inserted here */
return ContentView()
.environment(
\.managedObjectContext,
context
)
}
}
Where CoreDataManager is:
enum CoreDataManager {
static var context: NSManagedObjectContext {
persistentContainer.viewContext
}
static let persistentContainer: NSPersistentContainer = {
let container = NSPersistentContainer(name: "MyContainerName")
container.loadPersistentStores { description, error in
guard let error = error else { return }
fatalError("Core Data error: '\(error.localizedDescription)'.")
}
return container
}()
}
Not exactly sure why this helped, but now it works perfectly. Additionally you can add sample data to this context where I have marked with a comment.
This is my solution.
I don't want use CoreData in view. I want MVVM style.
So you need to mock Core data for display in Canvas view.
This is an example :
// View
struct MyView: View {
#ObservedObject var viewModel: PreviewViewModel
}
// View Model
final class MyViewModel: ObservableObject {
#Published var repository: RepositoryProtocol // CoreData
}
// Repository
protocol RepositoryProtocol { }
class Repository: RepositoryProtocol { ... }
class MockRepository: RepositoryProtocol { ... } // Create a Mock
// Init of your view
// If Canvas use mock
if ProcessInfo.processInfo.environment["XCODE_RUNNING_FOR_PREVIEWS"] == "1" {
repository = MockRepository()
// else App use Repository
} else {
repository = Repository.shared
}
let viewModel = MyViewModel(repository:repository)
MyViewModel(viewModel: viewModel)
This worked for me. In the AppDelegate create a different preview context and fill it with objects.
lazy var persistentContainerPreview: NSPersistentContainer = {
let persistentContainer = NSPersistentContainer(name: "MyModel")
persistentContainer.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error as NSError? {
}
})
let didCreateSampleData = UserDefaults.standard.bool(forKey: "didCreateSampleData")
if !didCreateSampleData {
let context = persistentContainer.viewContext
let recipe = Recipe(context: context)
recipe.title = "Soup 2"
recipe.difficultyName = "NOT TOO TRICKY"
recipe.difficultyValue = 1
recipe.heroImage = "dsfsdf"
recipe.ingredients = "meat"
recipe.method = "sdcsdsd"
recipe.published = Date()
recipe.recipeId = 1
recipe.servings = 4
recipe.tags = "sdfs"
recipe.totalTime = 100
recipe.totalTimeFormatted = "Less than 2 hours"
try! context.save()
}
return persistentContainer
}()
Then in your preview.
struct RecipeView_Previews: PreviewProvider {
static var previews: some View {
let context = (UIApplication.shared.delegate as! AppDelegate).persistentContainerPreview.viewContext
let recipe = try! context.fetch(Recipe.fetchRequest()).first as! Recipe
RecipeView(recipe: recipe).environment(\.managedObjectContext, context)
}
}
One option is to NOT use Core Data in previews. This is helpful enough to see the UI of what I'm building but I'll still need to use Simulator to test the functionality.
#if !DEBUG
// Core Data related code e.g. #FetchRequest
#endif
What was suggested in Previewing ContentView with CoreData worked for me, Xcode Version 11.0 (11A419c) Mac OS 10.15 Beta (19A558d). My crash logs showed an index error,
*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArray0 objectAtIndex:]: index 0 beyond bounds for empty NSArray'
because there was no data there, so I had to handle this unique "preview" case and that got things working.
It crashes because it was instructed so in the PersistenceController:
struct PersistenceController {
...
static var preview: PersistenceController = {
...
do {
try viewContext.save()
} catch {
// Replace this implementation with code to handle the error appropriately.
// fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
let nsError = error as NSError
fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
}
return result
}()
...
}
So the actual reason can be seen in the crash report. Actually, XCode 12.4 shows a warning about checking the crash report; however, the report is too verbose for a newbie like me from web development. Thus it took me a while to find out the problem, so I hope this would save some time for others.
...and the problem in my case was a required attribute was not set while populating the core data model for previews.
The thing is you need to find out which line cause the crash.
Since the canvas doesn't show the detailed error, using OSLog and Console.app to debug would be a possible solution.
For example:
import os.log
struct YourView_Previews: PreviewProvider {
static var previews: some View {
os_log("[DEBUG]-\(#function)---1--")
let moc = PersistenceController.preview.container.viewContext
os_log("[DEBUG]-\(#function)---2--")
let item = Item.previewData(context: moc)
os_log("[DEBUG]-\(#function)---3--")
return YourView(item: item, now: Date())
.environment(\.managedObjectContext, moc)
}
}
Remember to use filter to better catch the debug message from Console.
After finding out which line cause the crash, you can further look into the line and continue the process until you find the culprit.
(In my case, I forgot to add UUID to the preview data which causing the canvas to crash.)
I want to cast some Latin strings to English(PinYin) with swift on Linux，so I wrote a function, but it seems to have some errors in it. It can run in xcode on mac os, but it will go wrong on Linux. I think there are something wrong in the conversion
between CFString and string. I don't know what it is. Can someone help me? Thanks
import Foundation
#if os(Linux)
import CoreFoundation
import Glibc
#endif
public extension String{
func transformToLatinStripDiacritics() -> String{
let nsStr = NSMutableString(string: self)
let str = unsafeBitCast(nsStr, to: CFMutableString.self)
if CFStringTransform(str, nil, kCFStringTransformToLatin, false){
if CFStringTransform(str, nil, kCFStringTransformStripDiacritics, false){
let s = String(describing: unsafeBitCast(str, to: NSMutableString.self) as NSString)
return s
}
return self
}
return self
}
}
As far as I tried on the IBM Swift Sandbox, CFStringTransform does not work on arbitrary CFMutableStrings. Seems it requires CFMutableString based on UTF-16 representation.
import Foundation
#if os(Linux)
import CoreFoundation
import Glibc
#endif
public extension String {
func transformToLatinStripDiacritics() -> String{
let chars = Array(self.utf16)
let cfStr = CFStringCreateWithCharacters(nil, chars, self.utf16.count)
let str = CFStringCreateMutableCopy(nil, 0, cfStr)!
if CFStringTransform(str, nil, kCFStringTransformToLatin, false) {
if CFStringTransform(str, nil, kCFStringTransformStripDiacritics, false) {
return String(describing: str)
}
return self
}
return self
}
}
print("我在大阪住".transformToLatinStripDiacritics()) //->wo zai da ban zhu
Tested only for a few examples. So, this may not be the best solution for your issue.
Well I am trying to creating a simple tool to read an specific offset address from a file that's within the project.
I can read it fine and get the bytes, the problem is that I want to convert the result into a string, but I just can't.
My output is this: <00000100 88000d00 02140dbb 05c3a282> but I want into String.
Found some examples of doing it using an extension for NSData, but still didn't work.
So anyone could help??
Here's my code:
class ViewController: UIViewController {
let filemgr = NSFileManager.defaultManager()
override func viewDidLoad() {
super.viewDidLoad()
// Do any additional setup after loading the view, typically from a nib.
let pathToFile = NSBundle.mainBundle() .pathForResource("control", ofType: "bin")
let databuffer = filemgr.contentsAtPath(pathToFile!)
let file: NSFileHandle? = NSFileHandle(forReadingAtPath: pathToFile!)
if file == nil {
println("File open failed")
} else {
file?.seekToFileOffset(197584)
let byte = file?.readDataOfLength(16)
println(byte!)
file?.closeFile()
}
}
}
So long as you know the encoding, you can create a string from an NSData object like this
let str = NSString(data: data, encoding: NSUTF8StringEncoding)
By the way, you might want to try using if let to unwrap your optionals rather than force-unwrapping, to account for failure possibilities:
let filemgr = NSFileManager.defaultManager()
if let pathToFile = NSBundle.mainBundle() .pathForResource("control", ofType: "bin"),
databuffer = filemgr.contentsAtPath(pathToFile),
file = NSFileHandle(forReadingAtPath: pathToFile)
{
file.seekToFileOffset(197584)
let bytes = file.readDataOfLength(16)
let str = NSString(data: bytes, encoding: NSUTF8StringEncoding)
println(str)
file.closeFile()
}
else {
println("File open failed")
}
The correct answer following #Martin R suggestion to this link: https://codereview.stackexchange.com/a/86613/35991
Here's the code:
extension NSData {
func hexString() -> String {
// "Array" of all bytes:
let bytes = UnsafeBufferPointer<UInt8>(start: UnsafePointer(self.bytes), count:self.length)
// Array of hex strings, one for each byte:
let hexBytes = map(bytes) { String(format: "%02hhx", $0) }
// Concatenate all hex strings:
return "".join(hexBytes)
}
}
And I used like this:
let token = byte.hexString()