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Ensure value in a Dictionary
In many cases, I need to get the value from a dictionary given a key (usually a string). I have the following helper class: public class ObjectCache<T> { private var cache = [String: T]() subscript(name: String) -> T? { get { return cache[name] } set { cache[name] = newValue } } func get(_ name: String, with builder: () -> T?) -> T? { var obj = cache[name] if obj == nil { obj = builder() cache[name] = obj } return obj } } This saves much keyboard typing and avoid common errors of oversight. Like below: let serviceURL = self.urlCache.get(name) { return comp.url }! Now my question is - Does Swift provide some builtin functionality like this? I just hope I did not re-event the wheel.
1
0
375
Sep ’23
Need help on Array and API design
I am working on an app which I plan to submit to App Store in 2 weeks. Now I have a headache with Array type. I have the following API design in my app: class SomeParser { func getTranslations(_ locale: String) -> [TranslationUnit]? { // Check if the locale units are already in a cache, if not build a new list // and return the list } } class MainVC { func doTranslation() { var list = parser.getTranslation("en") // Modify some units in the list. // How to put it back to cache? } } Now the problem is that since Array is a value type, the modified list is isolated. The only way to reflect the changes into cache is put the modified list back to cache: translationCache[locale] = modifiedList But this is counter-intuitive and waste of performance. Is there anyway to workaround this problem?
1
0
417
Oct ’23
Need help on generics where clause
I have the following class: /// Act as a reference container for value types. public class ValueBox<ValueType: ??> { public var value: ValueType public init() { value = ValueType() // Compiler error } public init(_ value: ValueType) { self.value = value } } Is it possible to specify the generic type ValueType can be inited?
1
0
306
Oct ’23
PropertyListDecoder and .strings file
I have the following code: let file = "/path/to/en.lproj/Localizable.strings" let dec = PropertyListDecoder() var f: PropertyListSerialization.PropertyListFormat = .openStep do { //let data = strings.data(using: .utf8)! let data = try Data(contentsOf: URL(fileURLWithPath: file)) let list = try dec.decode([String: String].self, from: data, format: &f) print("foramt:", f.rawValue) list.forEach { print($0.key, $0.value) } } catch { print(error) } It seems PropertyListDecoder can correctly decode .strings file format; detected format is openStep (value is 1). But I am note sure because I couldn't find any docs on PropertyListDecoder about .strings file. Can anyone confirm this?
1
0
448
Oct ’23
Is it safe to call low level Darwin function on FileHandle?
I have the following code: extension FileHandle { func readInto(_ buffer: inout [UInt8]) -> Int { buffer.withUnsafeMutableBytes { Darwin.read(fileDescriptor, $0.baseAddress, $0.count) } } } It can compile, but I wonder if this is supported since it's code in an app that is going to be submitted to App Store. The reason I don't use read(upToCount:) or readData(ofLength:) is that I am reading possibly very large files by small chunks and don't want to let Swift runtime allocate small buffers repeatedly.
0
0
317
Nov ’23
How read image file metadata?
I want to read metadata of image files such as copyright, author etc. I did a web search and the closest thing is CGImageSourceCopyPropertiesAtIndex: - (void)tableViewSelectionDidChange:(NSNotification *)notif { NSDictionary* metadata = [[NSDictionary alloc] init]; //get selected item NSString* rowData = [fileList objectAtIndex:[tblFileList selectedRow]]; //set path to file selected NSString* filePath = [NSString stringWithFormat:@"%@/%@", objPath, rowData]; //declare a file manager NSFileManager* fileManager = [[NSFileManager alloc] init]; //check to see if the file exists if ([fileManager fileExistsAtPath:filePath] == YES) { //escape all the garbage in the string NSString *percentEscapedString = (NSString *)CFURLCreateStringByAddingPercentEscapes(NULL, (CFStringRef)filePath, NULL, NULL, kCFStringEncodingUTF8); //convert path to NSURL NSURL* filePathURL = [[NSURL alloc] initFileURLWithPath:percentEscapedString]; NSError* error; NSLog(@"%@", [filePathURL checkResourceIsReachableAndReturnError:error]); //declare a cg source reference CGImageSourceRef sourceRef; //set the cg source references to the image by passign its url path sourceRef = CGImageSourceCreateWithURL((CFURLRef)filePathURL, NULL); //set a dictionary with the image metadata from the source reference metadata = (NSDictionary *)CGImageSourceCopyPropertiesAtIndex(sourceRef,0,NULL); NSLog(@"%@", metadata); [filePathURL release]; } else { [self showAlert:@"I cannot find this file."]; } [fileManager release]; } Is there any better or easy approach than this?
1
0
966
Dec ’23
Environment variable not working in another user account
I have the following in my .zshrc: export MY_LIBRARY_DIR=~/bin In Xcode I can set header/lib search path using something like $(MY_LIBRARY_DIR)/abc. This works fine in my daily used user account. But today I found that this technique does not work in a test user account (for testing purpose only). I even reboot my machine but still can't get it working. Am I missing something very obvious??? BTW, I am using Xcode 14.2 and 14.3.1.
1
0
725
Dec ’23
How detect cyclic symbolic links using NSFileManager?
My code is crashing Xcode (or even macOS kernel) during debugging - Xcode just vanishes from screen! // pseudo code public func hunt(in directory: URL) { let fileIterator = fileMan.enumerator(at: directory) // collect app packages into a list var packages = [URL]() for case let fileURL as URL in fileIterator { if fileURL.pathExtension == "app" { packages.append(fileURL) } } // FileWrappers var wrappers = [FileWrappers]() for packageURL in packages { //!!! The line below eventually crashes Xcode (or even macOS kernel once)! wrappers[packageURL] = try? FileWrapper(url: packageURL, options: .immediate) // NOTE: I need FileWrapper.matchesContents later in some code } } // unit test case func test() {} myObj.hunt(in: URL(fileURLWithPath: "/Applications")) } I suspect that the FileWrapper constructor is traversing directories and encounter cyclic symbolic links and eventually it crashes; since it's running at system runtime level, most probably it also crashes macOS kernel! So my question is that is there any way to detect cyclic symbolic links so that I can design my own logics similar to FileWrapper?
2
0
561
Jan ’24
Is there any builtin Text Find Bar?
I have a NSTableView which shows a list of translated text items. I want to provide a Find Bar for user to filter through the items, like the one I have in Xcode. Of course I don't want so many features; I only want to let user enter some text.
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2
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0
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621
Activity
Sep ’23
How to implement similar navigation bar like what we have in Xcode?
Can anyone give any clues about how the navigation bar is implemented like below?
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0
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0
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454
Activity
Sep ’23
Ensure value in a Dictionary
In many cases, I need to get the value from a dictionary given a key (usually a string). I have the following helper class: public class ObjectCache<T> { private var cache = [String: T]() subscript(name: String) -> T? { get { return cache[name] } set { cache[name] = newValue } } func get(_ name: String, with builder: () -> T?) -> T? { var obj = cache[name] if obj == nil { obj = builder() cache[name] = obj } return obj } } This saves much keyboard typing and avoid common errors of oversight. Like below: let serviceURL = self.urlCache.get(name) { return comp.url }! Now my question is - Does Swift provide some builtin functionality like this? I just hope I did not re-event the wheel.
Replies
1
Boosts
0
Views
375
Activity
Sep ’23
Need help on Array and API design
I am working on an app which I plan to submit to App Store in 2 weeks. Now I have a headache with Array type. I have the following API design in my app: class SomeParser { func getTranslations(_ locale: String) -> [TranslationUnit]? { // Check if the locale units are already in a cache, if not build a new list // and return the list } } class MainVC { func doTranslation() { var list = parser.getTranslation("en") // Modify some units in the list. // How to put it back to cache? } } Now the problem is that since Array is a value type, the modified list is isolated. The only way to reflect the changes into cache is put the modified list back to cache: translationCache[locale] = modifiedList But this is counter-intuitive and waste of performance. Is there anyway to workaround this problem?
Replies
1
Boosts
0
Views
417
Activity
Oct ’23
Need help on generics where clause
I have the following class: /// Act as a reference container for value types. public class ValueBox<ValueType: ??> { public var value: ValueType public init() { value = ValueType() // Compiler error } public init(_ value: ValueType) { self.value = value } } Is it possible to specify the generic type ValueType can be inited?
Replies
1
Boosts
0
Views
306
Activity
Oct ’23
PropertyListDecoder and .strings file
I have the following code: let file = "/path/to/en.lproj/Localizable.strings" let dec = PropertyListDecoder() var f: PropertyListSerialization.PropertyListFormat = .openStep do { //let data = strings.data(using: .utf8)! let data = try Data(contentsOf: URL(fileURLWithPath: file)) let list = try dec.decode([String: String].self, from: data, format: &f) print("foramt:", f.rawValue) list.forEach { print($0.key, $0.value) } } catch { print(error) } It seems PropertyListDecoder can correctly decode .strings file format; detected format is openStep (value is 1). But I am note sure because I couldn't find any docs on PropertyListDecoder about .strings file. Can anyone confirm this?
Replies
1
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0
Views
448
Activity
Oct ’23
Common audio/image file extensions on macOS
I have a need to list all known audio/image file types in a planned app. What I have known so far: images .apng .avi, .avif .gif .jpg, .jpeg, .jfif, .pjpeg, .pjp .png .svg .webp audio .aif .cda .mid, .midi .mp3 .mpa .ogg .wav .wma What are the missing ones?
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2
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0
Views
910
Activity
Dec ’23
Is it safe to call low level Darwin function on FileHandle?
I have the following code: extension FileHandle { func readInto(_ buffer: inout [UInt8]) -> Int { buffer.withUnsafeMutableBytes { Darwin.read(fileDescriptor, $0.baseAddress, $0.count) } } } It can compile, but I wonder if this is supported since it's code in an app that is going to be submitted to App Store. The reason I don't use read(upToCount:) or readData(ofLength:) is that I am reading possibly very large files by small chunks and don't want to let Swift runtime allocate small buffers repeatedly.
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0
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0
Views
317
Activity
Nov ’23
How parse byte size strings into actual number?
I want to convert byte size strings like "1234kb", "100mb" or "5gb" to their actual number representation. Is there any builtin functions for this purpose?
Replies
2
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0
Views
461
Activity
Nov ’23
How read image file metadata?
I want to read metadata of image files such as copyright, author etc. I did a web search and the closest thing is CGImageSourceCopyPropertiesAtIndex: - (void)tableViewSelectionDidChange:(NSNotification *)notif { NSDictionary* metadata = [[NSDictionary alloc] init]; //get selected item NSString* rowData = [fileList objectAtIndex:[tblFileList selectedRow]]; //set path to file selected NSString* filePath = [NSString stringWithFormat:@"%@/%@", objPath, rowData]; //declare a file manager NSFileManager* fileManager = [[NSFileManager alloc] init]; //check to see if the file exists if ([fileManager fileExistsAtPath:filePath] == YES) { //escape all the garbage in the string NSString *percentEscapedString = (NSString *)CFURLCreateStringByAddingPercentEscapes(NULL, (CFStringRef)filePath, NULL, NULL, kCFStringEncodingUTF8); //convert path to NSURL NSURL* filePathURL = [[NSURL alloc] initFileURLWithPath:percentEscapedString]; NSError* error; NSLog(@"%@", [filePathURL checkResourceIsReachableAndReturnError:error]); //declare a cg source reference CGImageSourceRef sourceRef; //set the cg source references to the image by passign its url path sourceRef = CGImageSourceCreateWithURL((CFURLRef)filePathURL, NULL); //set a dictionary with the image metadata from the source reference metadata = (NSDictionary *)CGImageSourceCopyPropertiesAtIndex(sourceRef,0,NULL); NSLog(@"%@", metadata); [filePathURL release]; } else { [self showAlert:@"I cannot find this file."]; } [fileManager release]; } Is there any better or easy approach than this?
Replies
1
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0
Views
966
Activity
Dec ’23
Is there any way to get static var's in a type using Mirror?
Does Swift support this? Til now my understanding is that reflection only works with public members. Is it possible to get private/static members of a type?
Replies
2
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0
Views
524
Activity
Dec ’23
Environment variable not working in another user account
I have the following in my .zshrc: export MY_LIBRARY_DIR=~/bin In Xcode I can set header/lib search path using something like $(MY_LIBRARY_DIR)/abc. This works fine in my daily used user account. But today I found that this technique does not work in a test user account (for testing purpose only). I even reboot my machine but still can't get it working. Am I missing something very obvious??? BTW, I am using Xcode 14.2 and 14.3.1.
Replies
1
Boosts
0
Views
725
Activity
Dec ’23
Is there any way to tell if a file is on SSD volume?
I have a need to optimize reading strategy, based on if the file is on hard disk or SSD. Does macOS provide any low-level API so that I can query such information?
Replies
2
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0
Views
610
Activity
Jan ’24
Weird source code problem of a specific file
After upgrading to Xcode 15.1 on Sonoma, I get a very weird problem in an on-going project. This source file has no syntax coloring. No matter how I try "Open As->Source Code" it just won't work. All other files (sources/resources) work fine. Is this a known bug? Is there any way to get syntax coloring back?
Replies
1
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0
Views
448
Activity
Jan ’24
How detect cyclic symbolic links using NSFileManager?
My code is crashing Xcode (or even macOS kernel) during debugging - Xcode just vanishes from screen! // pseudo code public func hunt(in directory: URL) { let fileIterator = fileMan.enumerator(at: directory) // collect app packages into a list var packages = [URL]() for case let fileURL as URL in fileIterator { if fileURL.pathExtension == "app" { packages.append(fileURL) } } // FileWrappers var wrappers = [FileWrappers]() for packageURL in packages { //!!! The line below eventually crashes Xcode (or even macOS kernel once)! wrappers[packageURL] = try? FileWrapper(url: packageURL, options: .immediate) // NOTE: I need FileWrapper.matchesContents later in some code } } // unit test case func test() {} myObj.hunt(in: URL(fileURLWithPath: "/Applications")) } I suspect that the FileWrapper constructor is traversing directories and encounter cyclic symbolic links and eventually it crashes; since it's running at system runtime level, most probably it also crashes macOS kernel! So my question is that is there any way to detect cyclic symbolic links so that I can design my own logics similar to FileWrapper?
Replies
2
Boosts
0
Views
561
Activity
Jan ’24