It's a stupid question. I found out why. I set this up several years ago and I forgot the exact steps. Actually I have to define a custom path in Xcode Preferences->Locations->Custom Paths.

Well, it's partially true. Playground: print("class:") let m1 = Mirror(reflecting: Some.self) for child in m1.children { print(child.label ?? "", child.value) } print("instance:") let m2 = Mirror(reflecting: Some()) for child in m2.children { print(child.label ?? "", child.value) } print("\n-=|E.O.F|=-") class Some { static let inst = Some() private var n = 1234 var f = 1.234 } Output: class: instance: n 1234 f 1.234 Mirror can't mirror the static variable.

After some digging, it seems the command line tool mdls does similar job: mdls IMG_0245.jpeg _kMDItemDisplayNameWithExtensions = "IMG_0245.jpeg" kMDItemAcquisitionMake = "Apple" ... kMDItemContentType = "public.jpeg" ... But I prefer achieving these information by coding. Any ideas?

For other peoples reference, I have found the answer in this thread, thanks to Quinn's reply.

Yes! That's just what I need. if let ut = UTType.types(tag: "jpeg", tagClass: .filenameExtension, conformingTo: nil).first { print(ut.tags[.filenameExtension]) }

Actually I don't have 'a lot' examples. I just started real app development using Swift a couple of months ago. For this specific scenario, I really like to have what I have in C/C++. Advantages: It can save a few key strokes and makes me as a developer feel better; and even more, makes Swift feels more swift. auto n = 12345ull; vs var n: UInt64 = 12345 Real world example (unit test): func testByteSize() { let tests = [ (s: "1234", v: 1234), (s: "1kb", v: 1024), (s: "1234k", v: 1234 * 1024), (s: "3mb", v: 3 * 1024 * 1024), (s: "2GB", v: 2 * 1024 * 1024 * 1024), (s: "7tb", v: 7 * 1024 * 1024 * 1024 * 1024), ] for test in tests { let n = test.s.parseByteSize() XCTAssertNotNil(n) XCTAssertEqual(UInt64(test.v), n!) } } If Swift allows me to code a number as 1234ull, I won't have to do the UInt64(test.v) cast. Moreover, I really like the tuple's v field be UInt64 instead of default Int.

It seems I can use the builtin Scanner class: public extension String { func parseByteSize() -> UInt64? { var n: UInt64 = 0 let scanner = Scanner(string: self) if scanner.scanUnsignedLongLong(&n) { if !scanner.isAtEnd { let suffix = self[self.index(self.startIndex, offsetBy: scanner.scanLocation)...] switch suffix.uppercased() { case "KB": n *= 1024 case "MB": n *= 1024 * 1024 case "GB": n *= 1024 * 1024 * 1024 case "TB": n *= 1024 * 1024 * 1024 * 1024 default: return nil } } return n } return nil } }

After some digging on the net, I myself found a solution: NSStringEncoding gbkEncoding = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000); NSString* newStr = [[NSString alloc] initWithData:data encoding:gbkEncoding];

Does anyone know where I can find the specification of strings file format? Currently by pure observing, I believe the value part of key-value pair is very similar or same with C/JavaScript string syntax. Say, \n and " are escaped, but not sure if there are other specials.

It's strange that I can run FileMerge via command line opendiff file1 file2.

Is there any way to specify ValueType is a value type in the where clause? Apparently you don't need a box if the value is already a reference type.

It's an agony working with array/dictionary in Swift! NSMutableArray does not support generics so I have to stick to Swift builtin array. I finally have to employ a not-so-perfect-and-ugly workaround: /// Act as a reference container for value types. open class ValueBox<ValueType> { public var value: ValueType public init(_ value: ValueType) { self.value = value } } // Arrays in a dictionary typealias TranslationUnitBox = ValueBox<[TranslationUnit]> var translations = [String: TranslationUnitBox>() // Later in some other code if let box = translations["en"] { box.value[index].translatedText = "..." }

I found the answer myself. It's a misunderstanding of ATS (Apple Transport Security) feature. I thought only non-HTTPS protocol needs the following ATS in info.plist: <key>NSAppTransportSecurity</key> <dict> <key>NSAllowsArbitraryLoads</key> <true/> </dict> But it turned out that connecting to HTTPS also needs the above setting.

Okay, I just found answer myself - NSSearchField

I found a solution myself. I need to force unwrap the newValue like below: willSet { // this guarantees newValue is not nil let _ = newValue! }