Swift 4 introduced a family of concrete Key-Path types, a new Key-Path Expression to produce them and a new closure-based observe function available to classes that inherit NSObject. Using this new set of features, your particular example can now be expressed much more succinctly: self.observation = object.observe(\.keyPath) { [unowned self] object, change in self.someFunction() } … Read more
There’s a subtle, but important difference between these two lines of code: // Exhibit 1 foo = try container.decode(Int?.self, forKey: .foo) // Exhibit 2 foo = try container.decodeIfPresent(Int.self, forKey: .foo) Exhibit 1 will parse: { “foo”: null, “bar”: “something” } but not: { “bar”: “something” } while exhibit 2 will happily parse both. So in … Read more
The error is telling you that as of iOS 12 the old UIImageJPEGRepresentation function has been replaced with the new jpegData method on UIImage. Change: let imageData = UIImageJPEGRepresentation(image, 0.75) to: let imageData = image.jpegData(compressionQuality: 0.75) Similarly, the use of UIImagePNGRepresentation has been replaced with pngData().
Well as the other guys also explained that braces are a must in swift. But for simplicity one can always do something like: let a = -5 // if the condition is true then doThis() gets called else doThat() gets called a >= 0 ? doThis(): doThat() func doThis() { println(“Do This”) } func doThat() … Read more
In Swift 3 you can omit the associated value of type Void: let res: Result<Void> = .success() In Swift 4 you have to pass an associated value of type Void: let res: Result<Void> = .success(()) // Or just: let res = Result.success(())
I think this ‘bug’ may be a Swift 4 “feature”, specifically something they call “Exclusive access to Memory”. Check out this WWDC video. Around the 50-minute mark, the long-haired speaker explains it. https://developer.apple.com/videos/play/wwdc2017/402/?time=233 You could try turning the thread sanitizer off in your scheme settings if you’re happy to ignore it. However, the debugger is … Read more
A bit late to the party, but I’ve stumbled upon a way of getting a key path string from NSObject subclasses at least: NSExpression(forKeyPath: \UIView.bounds).keyPath
You can use the Codable interface with CoreData objects to encode and decode data, however it’s not as automatic as when used with plain old swift objects. Here’s how you can implement JSON Decoding directly with Core Data objects: First, you make your object implement Codable. This interface must be defined on the object, and … Read more
The reason why your first example doesn’t compile (and your second crashes) is because protocols don’t conform to themselves – Tag is not a type that conforms to Codable, therefore neither is [Tag]. Therefore Article doesn’t get an auto-generated Codable conformance, as not all of its properties conform to Codable. Encoding and decoding only the … Read more
In Swift 5 there is a simple one-liner to get the number of days (or any other DateComponent) between two dates: let diffInDays = Calendar.current.dateComponents([.day], from: dateA, to: dateB).day Note: As pointed out in the comments, this solution measures the 24h periods and therefore requires at least 24h between dateA and dateB.