Why Ternary operator in not called a binary Operator or ternary Operands ?
question ? answer1 : answer2
When it takes 2 operators ?
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Hello,
This test code for creating an array using a loop works:
var quotes: [(id: String, name: String)] {
var output: [(id: String, name: String)] = []
for i in 1...numberOfRows {
let item: (id: String, name: String) = ("\(i)", "Name \(i)")
output.append(item)
}
return output
}
But if I try to apply this logic to retrieving data from a web service using the below code I am getting 2 errors:
For the line “quotes.append(item)” I am getting the error message “Cannot use mutating member on immutable value: ‘quotes’ is a get-only property."
For the line “return output” I am getting the error message “Cannot find ‘output’ in scope."
if let url = URL(string:"https://www.TEST.com/test_connection.php"){
URLSession.shared.dataTask(with: url) { (data, response, error) in
if let data = data{
if let json = try? JSONDecoder().decode([[String:String]].self, from: data){
json.forEach { row in
var item: (id: String, name: String) = ("test id value", "test name value")
quotes.append(item)
}
return output
}
}
}
}
Topic:
Programming Languages
SubTopic:
Swift
Crash Log
We have a issue with our watch app. When we do a release build with xcode 16 the watch app will not launch and crashes on watchOS 10 and below devices.
It does not do this on debug builds...and it does not do this on xcode 15 release/debug builds.
Anybody running into watch crashes on xcode 16?
Thanks
I want to know how to format doubles. In the program I have 4.3333 I just want to print 4 to the screen. I just want to print whole numbers. I'm using Swiftui with xcode. Please help. Thank you.
Topic:
Programming Languages
SubTopic:
Swift
Hello, I have a problem with the .onMove function. I believe I have set everything up properly. However, the moving does not seem to be working correctly. When I try to move the item, it is highlighted first, as it is supposed to be. Then, while I am moving it through the list, it disappears for some reason, and at the end of the move, it comes back to its initial place. (I use iOS 16.0 minimum, so I don't have to include the EditButton(). It works the same in the edit mode tho)
import SwiftUI
struct Animal: Identifiable {
var id = UUID()
var name: String
}
struct ListMove: View {
@State var animals = [Animal(name: "Dog"), Animal(name: "Cat"), Animal(name: "Cow"), Animal(name: "Goat"), Animal(name: "Chicken")]
var body: some View {
List {
ForEach(animals) { animal in
Text(animal.name)
}
.onMove(perform: move)
}
}
func move(from source: IndexSet, to destination: Int) {
animals.move(fromOffsets: source, toOffset: destination)
}
}
#Preview {
ListMove()
}
Hello,
I was expecting the code below to print the test message "line 25" because the class "API" is being called on line 57. But "line 25" is not being displayed in the debug window, please could you tell me why?
This is the debugging window:
line 93
0
line 93
0
line 93
0
import UIKit
// not sure these 2 below are needed
import SwiftUI
import Combine
struct NewsFeed: Codable {
var id: String
var name: String
var country: String
var type: String
var situation: String
var timestamp: String
}
let urlString = "https://www.notafunnyname.com/jsonmockup.php"
let url = URL(string: urlString)
let session = URLSession.shared
class API: ObservableObject {
let dataTask = session.dataTask(with: url!) { (data, response, error) in
print("line 25")
var dataString = String(data: data!, encoding: String.Encoding.utf8)
if error == nil && data != nil {
// Parse JSON
let decoder = JSONDecoder()
do {
var newsFeed = try decoder.decode([NewsFeed].self, from: data!)
print("line 38")
// print(newsFeed)
// print("line 125")
// print(newsFeed.count)
print(error)
}
catch{
print("Line 46, Error in JSON parsing")
print(error)
}
}
}.resume
// Make the API Call - not sure why but error clears if moved to line above
// dataTask.resume()
}
let myAPIarray = API()
class QuoteTableViewController: UITableViewController {
var newsFeed: [[String: String]] = []
override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
// let selectedQuote = quotes[indexPath.row]
// performSegue(withIdentifier: "moveToQuoteDetail", sender: selectedQuote)
}
override func viewDidLoad() {
super.viewDidLoad()
// tableView.dataSource = self
}
// Uncomment the following line to preserve selection between presentations
// self.clearsSelectionOnViewWillAppear = false
// Uncomment the following line to display an Edit button in the navigation bar for this view controller.
// self.navigationItem.rightBarButtonItem = self.editButtonItem
// MARK: - Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {
// #warning Incomplete implementation, return the number of sections
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
// (viewDidLoad loads after tableView)
// #warning Incomplete implementation, return the number of rows
print("line 93")
print(newsFeed.count)
return 10
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
// let cell = tableView.dequeueReusableCell(withIdentifier: "reuseIdentifier", for: indexPath)
let cell = UITableViewCell ()
cell.textLabel?.text = "test"
return cell
}
/*
// Override to support conditional editing of the table view.
override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
// Return false if you do not want the specified item to be editable.
return true
}
*/
/*
// Override to support editing the table view.
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
if editingStyle == .delete {
// Delete the row from the data source
tableView.deleteRows(at: [indexPath], with: .fade)
} else if editingStyle == .insert {
// Create a new instance of the appropriate class, insert it into the array, and add a new row to the table view
}
}
*/
/*
// Override to support rearranging the table view.
override func tableView(_ tableView: UITableView, moveRowAt fromIndexPath: IndexPath, to: IndexPath) {
}
*/
/*
// Override to support conditional rearranging of the table view.
override func tableView(_ tableView: UITableView, canMoveRowAt indexPath: IndexPath) -> Bool {
// Return false if you do not want the item to be re-orderable.
return true
}
*/
// MARK: - Navigation
// In a storyboard-based application, you will often want to do a little preparation before navigation
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Get the new view controller using segue.destination.
// Pass the selected object to the new view controller.
// getPrice()
print("test_segue")
if let quoteViewController = segue.destination as? QuoteDetailViewController{
if let selectedQuote = sender as? String {
quoteViewController.title = selectedQuote
}
}
}
}
Topic:
Programming Languages
SubTopic:
Swift
Hello together,
since Xcode Version > 15 the following error handling causes following error "Pattern of type 'DecodingError' cannot match 'Never'
func getSupportedCountries() async {
// fetch all documents from collection "seasons" from firestore
let queryCountries = try? await db.collection("countries").getDocuments()
if queryCountries != nil {
self.countries = (queryCountries!.documents.compactMap({ (queryDocumentSnapshot) -> Country? in
let result = Result { try? queryDocumentSnapshot.data(as: Country.self) }
switch result {
case .success(let country):
if let country = country {
// A country value was successfully initialized from the DocumentSnapshot
self.errorMessage = nil
return country
}
else {
// A nil value was successfully initialized from the DocumentSnapshot,
// or the DocumentSnapshot was nil
self.errorMessage = "Document doesn't exist."
return nil
}
case .failure(let error):
// A Country value could not be initialized from the DocumentSnapshot
switch error {
case DecodingError.typeMismatch(_, let context):
self.errorMessage = "\(error.localizedDescription): \(context.debugDescription)"
case DecodingError.valueNotFound(_, let context):
self.errorMessage = "\(error.localizedDescription): \(context.debugDescription)"
case DecodingError.keyNotFound(_, let context):
self.errorMessage = "\(error.localizedDescription): \(context.debugDescription)"
case DecodingError.dataCorrupted(let key):
self.errorMessage = "\(error.localizedDescription): \(key)"
default:
self.errorMessage = "Error decoding document: \(error.localizedDescription)"
}
return nil
}
}))
} else {
self.errorMessage = "No documents in 'countries' collection"
return
}
}
the interesting part of the code where XCODE shows an error is from "switch error" downwards.
Does anyone of you have an idea what's wrong?
Ay help appreciated !
Thx, Peter
I’m working with Swift and encountered an issue when using the contains method on an array. The following code works fine:
let result = ["hello", "world"].contains(Optional("hello")) // ✅ Works fine
However, when I try to use the same contains method with the array declared in a separate constant(or variable), I get a compile-time error:
let stringArray = ["hello", "world"]
let result = stringArray.contains(Optional("hello")) // ❌ Compile-time error
The compiler produces the following error message:
Cannot convert value of type 'Optional<String>' to expected argument type 'String'
Both examples seem conceptually similar, but the second one causes a compile-time error, while the first one works fine.
This confuses me because I know that Swift automatically promotes a non-optional value to an optional when comparing it with an optional value. This means "hello" should be implicitly converted to Optional("hello") for the comparison.
What I understand so far:
The contains(_:) method is defined as:
func contains(_ element: Element) -> Bool
Internally, it calls contains(where:), as seen in the Swift source code:
🔗 Reference
contains(where:) takes a closure that applies the == operator for comparison.
Since Swift allows comparing String and String? directly (String is implicitly promoted to String? when compared with an optional), I expected contains(where:) to work the same way.
My Questions:
Why does the first example work, but the second one fails with a compile-time error?
What exactly causes this error in the second case, even though both cases involve comparing an optional value with a non-optional value?
Does contains(_:) behave differently when used with an explicit array variable rather than a direct array literal? If so, why?
I know that there are different ways to resolve this, like using nil coalescing or optional binding, but what I’m really looking for is a detailed explanation of why this issue occurs at the compile-time level.
Can anyone explain the underlying reason for this behavior?
I’m aware that Xcode version 26 beta 3 provides an option to enable Swift’s Approachable Concurrency feature at the project level. However, I’d like to achieve the same for a Swift Package. Could you please advise on how to enable Approachable Concurrency support specifically for a Swift Package?
I'm using xcode 16.1 withSwift. I want to know how to call a function passing in an array. Also I need to know how to declare the function receiving the array. I currently have:
func myfunc(costa: [Double]) {
}
I call it like this:
myfunc(costa:[ ])
It's an array of Doubles. I don't get any errors but the array is always empty. Please help. Thank you.
Topic:
Programming Languages
SubTopic:
Swift
I want to understand what the recommended way is for string interoperability between swift and c++. Below are the 3 ways to achieve it. Approach 2 is not allowed at work due to restrictions with using std libraries.
Approach 1:
In C++:
char arr[] = "C++ String";
void * cppstring = arr;
std::cout<<"before:"<<(char*)cppstring<<std::endl; // C++ String
// calling swift function and passing the void buffer to it, so that swift can update the buffer content
Module1::SwiftClass:: ReceiveString (cppstring, length);
std::cout<<"after:"<<(char*)cppstring<<std::endl; // SwiftStr
In Swift:
func ReceiveString (pBuffer : UnsafeMutableRawPointer , pSize : UInt ) -> Void
{
// to convert cpp-str to swift-str:
let swiftStr = String (cString: pBuffer.assumingMemoryBound(to: Int8.self));
print("pBuffer content: \(bufferAsString)");
// to modify cpp-str without converting:
let swiftstr:String = "SwiftStr"
_ = swiftstr.withCString { (cString: UnsafePointer<Int8>) in
pBuffer.initializeMemory(as: Int8.self, from: cString, count: swiftstr.count+1)
}
}
Approach 2:
The ‘String’ type returned from a swift function is received as ‘swift::String’ type in cpp. This is implicitly casted to std::string type. The std::string has the method available to convert it to char *.
void
TWCppClass::StringConversion ()
{
// GetSwiftString() is a swift call that returns swift::String which can be received in std::string type
std::string stdstr = Module1::SwiftClass::GetSwiftString ();
char * cstr = stdstr.data ();
const char * conststr= stdstr.c_str ();
}
Approach 3:
The swift::String type that is obtained from a swift function can be received in char * by directly casting the address of the swift::String. We cannot directly receive a swift::String into a char *.
void
TWCppClass::StringConversion ()
{
// GetSwiftString() is a swift call that returns swift::String
swift::String swiftstr = Module1::SwiftClass::GetSwiftString ();
// obtaining the address of swift string and casting it into char *
char * cstr = (char*)&swiftstr;
}
I've been teaching myself Objective-C and I wanted to start creating projects that don't use ARC to become better at memory management and learn how it all works. I've been attempting to build and run applications, but I'm not really sure where to start as modern iOS development is used with Swift and memory management is handled.
Is there any way to create modern applications that use Objective-C, UIKit, and not use ARC?
Context: SwiftUI TextField with a String for simple math using NSExpression.
I first prepare the input string to an extent but a malformed input using valid characters still fails, as expected. Let's say preparedExpression is "5--"
let expr = NSExpression(format: preparedExpression)
gives
FAULT: NSInvalidArgumentException: Unable to parse the format string "5-- == 1"; (user info absent)
How can I use NSExpression such that either the preparedExpression is pre-tested before asking for actual execution or the error is handled in a polite way that I can use to alert the user to try again.
Is there a Swift alternative to NSExpression that I've missed?
At least with macOS Sequoia 15.5 and Xcode 16.3:
$ cat test.cc
#include &lt;locale.h&gt;
#include &lt;string.h&gt;
#include &lt;xlocale.h&gt;
int main(void) {
locale_t l = newlocale(LC_ALL_MASK, "el_GR.UTF-8", 0);
strxfrm_l(NULL, "ό", 0, l);
return 0;
}
$ c99 test.c &amp;&amp; ./a.out
Assertion failed: (p-&gt;val == key), function lookup_substsearch, file collate.c, line 596.
Abort trap: 6
Hi, I have issue on build my react native project and got this error "Undefined symbol: _swift_willThrowTypedImpl" how can I fix it?
I have an @objC used for notification.
kTag is an Int constant, fieldBeingEdited is an Int variable.
The following code fails at compilation with error: Command CompileSwift failed with a nonzero exit code if I capture self (I edited code, to have minimal case)
@objc func keyboardDone(_ sender : UIButton) {
DispatchQueue.main.async { [self] () -> Void in
switch fieldBeingEdited {
case kTag : break
default : break
}
}
}
If I explicitly use self, it compiles, even with self captured:
@objc func keyboardDone(_ sender : UIButton) {
DispatchQueue.main.async { [self] () -> Void in
switch fieldBeingEdited { // <<-- no need for self here
case self.kTag : break // <<-- self here
default : break
}
}
}
This compiles as well:
@objc func keyboardDone(_ sender : UIButton) {
DispatchQueue.main.async { () -> Void in
switch self.fieldBeingEdited { // <<-- no need for self here
case self.kTag : break // <<-- self here
default : break
}
}
}
Is it a compiler bug or am I missing something ?
Hello, I have an issue with importing some .mp3 files into a swift playground project (in Xcode, not in the Playground app). They worked fine in the Xcode project, but for some reason playgrounds isn't able to find them. I imported them the exact same way as I did in the Xcode project.
I’m working on a project in Xcode 16.2 and encountered an issue where getAPI() with a default implementation in a protocol extension doesn’t show up in autocomplete. Here’s a simplified version of the code:
import Foundation
public protocol Repository {
func getAPI(from url: String?)
}
extension Repository {
public func getAPI(from url: String? = "https://...") {
getAPI(from: url)
}
}
final class _Repository: Repository {
func getAPI(from url: String?) {
// Task...
}
}
let repo: Repository = _Repository()
repo.getAPI( // Autocomplete doesn't suggest getAPI()
I’ve tried the following without success:
• Clean build folder
• Restart Xcode
• Reindexing
Is there something wrong with the code, or is this a known issue with Xcode 16.2? I’d appreciate any insights or suggestions.
I have a class object created dynamically using Runtime, and I want to release some manually allocated memory resources when this object is deallocated. To achieve this, I added a custom implementation of the dealloc method using the following code:
SEL aSel = NSSelectorFromString(@"dealloc");
class_addMethod(kvoClass, aSel, (IMP)custom_dealloc, method_getTypeEncoding(class_getInstanceMethod(kvoClass, aSel)));
However, I encountered some issues. If I don't call the superclass's dealloc method in the cus_dealloc function, the superclass's dealloc implementation will not be executed. On the other hand, if I explicitly call the superclass's dealloc method, the program crashes.
Here is the implementation of the cus_dealloc function:
void custom_dealloc(id self, SEL _cmd) {
// Release other memory
![]("https://developer.apple.com/forums/content/attachment/c7b0c16b-be23-4776-b8db-f22b661c5e7d" "title=iShot_2025-01-03_19.31.34.png;width=1080;height=1895")
Class superClass = class_getSuperclass(object_getClass(self));
void (*originIMP)(struct objc_super *, SEL, ...) = (void *)objc_msgSendSuper;
struct objc_super *objcSuper = &(struct objc_super){self, superClass};
originIMP(objcSuper, _cmd);
}
demo
Just read about the new @concurrent option coming to Swift 6.2 and lover it, but...
It just me, but I which these options would pick a case and stick with it...
@Sendable
@unchecked
@MainActor
@concurrent
@Observable
@ObservationIgnored