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

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
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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 have a simple shell script as follows:
#!/bin/bash
OUTPUT="network.$(date +'%d-%m-%y').info.txt"
SUPPORT_ID="emailaddress"
echo "---------------------------------------------------" > $OUTPUT
echo "Run date and time: $(date)" >> $OUTPUT
echo "---------------------------------------------------" >> $OUTPUT
ifconfig >> $OUTPUT
echo "---------------------------------------------------" >> $OUTPUT
echo "Network info written to file: $OUTPUT."
echo "Please email this file to: $SUPPORT_ID."
It just dumps the network config into a file. At some point I will have the file emailed out, but right now I'm just trying to figure out why the output looks like the following?
bash ./test.sh
.etwork info written to file: network.26-01-25.info.txt
.lease email this file to: emailaddress
Why in the world does the initial character of the last couple of "echo" commands get clipped and turned into periods? The echos for the output of the commands piped into the output file are fine. Strange...
Any ideas?
Topic:
Programming Languages
SubTopic:
General
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
Hello, everyone!
Help me please to find answer. I have two applications: App-1 with share extension and App-2 without it. From the second app I can open share extension via UIActivityViewController. But I need this extension in the second application to open immediately by pressing a button, and not through UIActivityViewController. Can I do this?
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
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?
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
I've got a watch app, still with storyboard, WKInterfaceController and WatchConnectivity.
After updating it for swift 6 concurrency I thought I'd keep it for a little while without swift 6 concurrency dynamic runtime check.
So I added -disable-dynamic-actor-isolation in OTHER_SWIFT_FLAGS, but it doesn't seem to have an effect for the Apple Watch target. Without manually marking callbacks where needed with @Sendable in dynamic checks seem to be in place.
swiftc invocation is as (includes -disable-dynamic-actor-isolation):
swiftc -module-name GeoCameraWatchApp -Onone -enforce-exclusivity\=checked ... GeoCameraWatchApp.SwiftFileList -DDEBUG -enable-bridging-pch -disable-dynamic-actor-isolation -D DEBUG -enable-experimental-feature DebugDescriptionMacro -sdk /Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS11.2.sdk -target arm64_32-apple-watchos7.0 -g -module-cache-path /Users/stand/Library/Developer/Xcode/DerivedData/ModuleCache.noindex -Xfrontend -serialize-debugging-options -enable-testing -index-store-path /Users/stand/Library/Developer/Xcode/DerivedData/speedo-almhjmryctkitceaufvkvhkkfvdw/Index.noindex/DataStore -enable-experimental-feature OpaqueTypeErasure -Xcc -D_LIBCPP_HARDENING_MODE\=_LIBCPP_HARDENING_MODE_DEBUG -swift-version 6
...
-disable-dynamic-actor-isolation flag seems to be working for the iOS targets, I believe.
The flag is described here
Am I missing something? Should the flag work for both iOS and Apple Watch targets?
I've created a Julia interface for Apple Accelerate's libSparse, via calling the library functions as if they were C (@ccall). I'm interested in using this in the context of power systems, where the sparse matrix is the Jacobian or the ABA matrix from a sparse grid network. However, I'm puzzled by the performance.
I ran a sampling profiler on repeated in-place solves of Ax = b for a large sparse matrix A and random dense vectors b. (A is size 30k, positive definite so Cholesky factorization.) The 2 functions with the largest impact are _SparseConvertFromCoordinate_Double from libSparse.dylib, and BLASStateRelease from libBLAS.dylib. That strikes me as bizarre. This is an in-place solve: there should be minimal overheard from allocating/deallocating memory. Also, it seems strange that the library would repeatedly convert from coordinate form. Is this expected behavior?
Thinking it might be an artifact of the Julia-C interface, I wrote up a similar program in C/Objective-C. I didn't profile it, but timing the same operation (repeated in-place solves of Ax = b for random vectors b, with the same matrix A as in the Julia) gave the same duration. I've attached the C/Objective-C below.profiling-comparison.m.txt
If you're familiar with Julia, the following will give you the matrix I was working with:
using PowerSystems, PowerNetworkMatrices
sys = System("pglib_opf_case30000_goc.m")
A = PowerNetworkMatrices.ABA_Matrix(sys).data
where you can find the .m file here. (As a crude way to transfer A from Julia to C, I wrote the 3 arrays A.nzval, A.colptr, and A.rowval to .txt files as space-separated lists of numbers: the above C/objective-C reads in those files.) To duplicate my Julia profiling, do pkg> add AppleAccelerate#libSparse Profile--note the #libSparse part, these features aren't on the main branch--then run
using AppleAccelerate, Profile
# run previous code snippet to define A
M, N = 10000, size(A)[1]
bs = [rand(N) for _ in 1:M]
aa_fact = AAFactorization(A)
factor!(aa_fact)
solve!(aa_fact, bs[1]) # pre-compile before we profile.
Profile.init(n = 10^6, delay = 0.0003)
@profile (for i in 1:M; solve!(aa_fact, bs[i]); end;)
Profile.print(C = true, format = :flat, sortedby = :count)
Hi all,
In Swift, I often see static helper functions grouped in an enum without any cases, like this:
enum StringUtils {
static func camelCaseToSnakeCase(_ input: String) -> String {
// implementation
}
}
Since this enum has no cases, it cannot be instantiated – which is exactly the point.
It’s meant to group related functionality without any stored state, and without the need for instantiation.
This pattern avoids writing a struct with a private init() and makes the intent clearer:
"This is just a static utility, not an object."
You’ll often see this used for things like:
AnalyticsEvents.track(_:)
My question:
Is this use of a case-less enum considered good practice in Swift when building static-only helpers?
Or is there a better alternative for expressing intent and preventing instantiation?
I’d appreciate any insight – especially if there’s official guidance or references from the Swift core team.
Thanks!
Topic:
Programming Languages
SubTopic:
Swift
I get this red warning in Xcode every time my app is syncing to the iCloud. My model has only basic types and enum that conform to Codable so i'm not sure what is the problem.
App is working well, synchronization works. But the warning doesn't look good.
Maybe someone has idea how to debug it.
We have FrameworkA which needs to use another FrameworkB internally to fetch a token.
Now when I try to use this FrameworkA, we are seeing an issue with internal framework i.e. No such module 'FrameworkB'.
But when I use @_implementationOnly import for the internal FrameworkB, I didn't see any issues.
So just wanted to check If I can go ahead and use this @_implementationOnly import flag in Production?
Why doesn’t deinit support async? At the end of a test, I want to wipe data from HealthKit, and it’s delete function is asynchronous.
I’m creating an app using SwiftUI, and I would like to incorporate a small Java codebase that I created for the Android version of the app. Is there a way to package the Java code to work on iOS and macOS
Topic:
Programming Languages
SubTopic:
General
The following code works when compiling for macOS:
print(NSMutableDictionary().isEqual(to: NSMutableDictionary()))
but produces a compiler error when compiling for iOS:
'NSMutableDictionary' is not convertible to '[AnyHashable : Any]'
NSDictionary.isEqual(to:) has the same signature on macOS and iOS. Why does this happen? Can I use NSDictionary.isEqual(_:) instead?
i am trying to build my code and have ran into this error.
"Trailing closure passed to parameter of type 'DispatchWorkItem' that does not accept a closure"
i have been trying to figure it out for so long, and even ai cant figure it out. is this a bug, or am i missing some obvious way to fix this ?
func loadUser(uid: String, completion: (() -> Void)? = nil) {
db.collection("users").document(uid).getDocument { [weak self] snapshot, error in
guard let data = snapshot?.data(), error == nil else { completion?(); return }
DispatchQueue.main.async {
self?.currentUser = User(
username: data["username"] as? String ?? "Learner",
email: data["email"] as? String ?? "",
profileImageName: "person.circle.fill",
totalXP: data["totalXP"] as? Int ?? 0,
currentStreak: data["currentStreak"] as? Int ?? 0,
longestStreak: data["longestStreak"] as? Int ?? 0,
level: data["level"] as? Int ?? 1,
levelProgress: data["levelProgress"] as? Double ?? 0.0,
xpToNextLevel: data["xpToNextLevel"] as? Int ?? 100,
completedLessons: data["completedLessons"] as? [String] ?? []
)
self?.saveUser()
completion?()
}
}
}
Last night my iPhone game crashed while running in debug mode on my iPhone. I just plugged it into my Mac, and was able to find the ips file. The stack trace shows the function in my app where it crashed, and then a couple of frames in libswiftCore.dylib before an assertion failure.
My question is - I've got absolutely no idea what the assertion failure actually was, all I have is...
0 libswiftCore.dylib 0x1921412a0 closure #1 in closure #1 in closure #1 in _assertionFailure(_:_:file:line:flags:) + 228
1 libswiftCore.dylib 0x192141178 closure #1 in closure #1 in _assertionFailure(_:_:file:line:flags:) + 327
2 libswiftCore.dylib 0x192140b4c _assertionFailure(_:_:file:line:flags:) + 183
3 MyGame.debug.dylib 0x104e52818 SentryBrain.takeTurn(actor:) + 1240
...
How do I figure out what the assertion failure was that triggered the crash? How do I figure out what line of code in takeTurn(...) triggered the failing assertion failure?
Hi the below array and code to output a list item works fine:
var quotes = [
[
"quote": "I live you the more ...",
"order": "1"
],
[
"quote": "There is nothing permanent ...",
"order": "2"
],
[
"quote": "You cannot shake hands ...",
"order": "3"
],
[
"quote": "Lord, make me an instrument...",
"order": "4"
]
]
cell.textLabel?.text = quotes[indexPath.row]["quote"]
However if I change the "order" values to be numbers rather than text like below then for the above line I get an error message in Xcode "No exact matches in call to subscript". Please could someone tell me how to make it work with the numbers stored as numbers? (I'm wondering if creating an any array type and using the .text function has caused a conflict but I can't find how to resolve)
[
"quote": "I live you the more ...",
"order": 1
],
[
"quote": "There is nothing permanent ...",
"order": 2
],
[
"quote": "You cannot shake hands ...",
"order": 3
],
[
"quote": "Lord, make me an instrument...",
"order": 4
]
]
Thank you for any pointers :-)
I've been testing my open source libraries with Swift 6.2 and the new Default Actor Isolation concurrency build setting set to MainActor (with Complete strict concurrency turned on). My library Destinations uses protocols extensively, often applying conformance to foundational Swift protocols like Hashable and Identifiable. Many of these basic protocols are not flagged as running on the @MainActor in Beta 1, leading to situations like this:
Given this example code:
public protocol Contentable: Identifiable {
var id: UUID { get }
}
final class ContentModel: Contentable {
let id: UUID = UUID()
}
I get the warning:
Multiline
Conformance of 'ContentModel' to protocol 'Contentable' crosses into main actor-isolated code and can cause data races; this is an error in the Swift 6 language mode
The fix it suggests is to put a @MainActor before the Contentable protocol declaration in ContentModel, which seems to be a new attribute configuration in Swift 6.2. This solves the warning, but would create a lot of extra noise across the codebase.
Was it an oversight or a temporary omission that protocols like Hashable and Identifiable do not run on @MainActor by default, or is there some other reason they are excluded? Considering how often protocols in our code may conform to foundational protocols like this, it seems at odds to the MainActor mode of the Default Actor Isolation setting given that it was created to make concurrency easier and less boilerplate to implement.