swift5

问题 After reading this article https://www.sqlite.org/rtree.html about the R*Tree in SQLite, i am currently experimenting with a 2-Dim R-Tree in a Core Data model. Particularly i expected (maybe somewhat naively) some kind of select statement on the index table but i did not see any in the SQLite debug trace when executing a fetch statement on the Region entity with indexed attributes (see predicateBoundaryIdx in the code below). My questions are: how must a Core Data model (entities, attributes)

问题 I am learning Swift as I go. I found functions like this viewDidLoad() and many others are sometimes written like this: override func viewDidLoad() { super.viewDidLoad() // Do any additional setup after loading the view, typically from a nib. } and sometimes written like this: override func viewDidLoad() { // Do any additional setup after loading the view, typically from a nib. super.viewDidLoad() } I mean with the call to super.viewDidLoad() as the first thing or as the last thing inside the

问题 Ive make a mini app with just a button and a picker and the idea is to have a done button above the picker so once ive chosen a value i can press done and the picker will close. I am aware if you click the "click me" button it will open and if you click it again close the picker but im looking for a button that appears with the picker and disapears with the clicker when clicked. Almost like a toolbar above the picker with a done button @State var expand = false @State var list = ["value1",

问题 I'm trying to use UIImagePickerController. It used to work fine but suddenly stopped working. Currently, I have inconsistent results(it sometimes works but sometimes doesn't). Here are methods related to UIIMagePickerController. What is wrong? @IBAction func uploadImageTapped(_ sender: UIButton) { let pickerView = UIImagePickerController() // Set cameraroll sor chooseing a photo // choose '.camera' if you want to take the picture pickerView.delegate = self pickerView.sourceType =

问题 I'm trying to use UIImagePickerController. It used to work fine but suddenly stopped working. Currently, I have inconsistent results(it sometimes works but sometimes doesn't). Here are methods related to UIIMagePickerController. What is wrong? @IBAction func uploadImageTapped(_ sender: UIButton) { let pickerView = UIImagePickerController() // Set cameraroll sor chooseing a photo // choose '.camera' if you want to take the picture pickerView.delegate = self pickerView.sourceType =

问题 I'm a swift learner. I work with SwiftUI which is a struct, I have to implement a WKWebView and in that, a url is changing dynamically. I have to catch these changing urls, but solutions I have tried are not working. For example: https://stackoverflow.com/a/48273950/10088243 I tried this code block but it is not working and it gives me some compiler errors: import SwiftUI import WebKit struct ContentView: UIViewRepresentable, WKNavigationDelegate { let request = URLRequest(url: URL(string:

问题 class A { let val : Int init(val: Int) { self.val = val } } I have these 3 strings: let className = "A" let argName = "val" let argValue = "4" How can I call A(val:4) from using these 3 strings? 回答1: Since you've noted in the comments that the types will all be subclasses of some supertype, then that supertype can handle all the dispatching. In Cocoa, this is a pretty common pattern known as a class cluster. class SuperA { enum SuperAError: Error { case cannotConstruct } static func create

问题 class A { let val : Int init(val: Int) { self.val = val } } I have these 3 strings: let className = "A" let argName = "val" let argValue = "4" How can I call A(val:4) from using these 3 strings? 回答1: Since you've noted in the comments that the types will all be subclasses of some supertype, then that supertype can handle all the dispatching. In Cocoa, this is a pretty common pattern known as a class cluster. class SuperA { enum SuperAError: Error { case cannotConstruct } static func create

问题 I have this code that I need to make reusable by other apps. This code shows messages where the localized app's name is present. So, I have localized strings like this: "DoYou" = "Do you really want to close $$$?"; "Quit" = "Quit $$$"; "Keep Running" = "Keep $$$ Running"; Where $$$ must be replaced with the localized app's name at run time. Because I want to learn about property wrappers, I have tried to create this one: extension String { func findReplace(_ target: String, withString: String

问题 I have this code that I need to make reusable by other apps. This code shows messages where the localized app's name is present. So, I have localized strings like this: "DoYou" = "Do you really want to close $$$?"; "Quit" = "Quit $$$"; "Keep Running" = "Keep $$$ Running"; Where $$$ must be replaced with the localized app's name at run time. Because I want to learn about property wrappers, I have tried to create this one: extension String { func findReplace(_ target: String, withString: String