swift-playground

问题 I'm experimenting code from https://alanquatermain.me/programming/swiftui/2019-11-15-CoreData-and-bindings/ my goal is to have DatePicker bind to Binding< Date? > which allow for nil value instead of initiate to Date(); this is useful, if you have Date attribute in your core data model entity which accept nil as valid value. Here is my swift playground code: extension Binding { init<T>(isNotNil source: Binding<T?>, defaultValue: T) where Value == Bool { self.init(get: { source.wrappedValue !=

问题 Is there a way to increase execution speed of a playground? I want to iterate many cycles and not to wait 10 minutes. For example: import UIKit var count = 0 for var i = 0; i < 1000000000; i++ { count++ } This code will execute a way too long. But I want to get quick result. 回答1: One of the biggest performance killer is the output at the right side of the playground. Now I will show you how to minimize this output. See at the end for your example code. Best Performance The most performant way

问题 Is there a way to increase execution speed of a playground? I want to iterate many cycles and not to wait 10 minutes. For example: import UIKit var count = 0 for var i = 0; i < 1000000000; i++ { count++ } This code will execute a way too long. But I want to get quick result. 回答1: One of the biggest performance killer is the output at the right side of the playground. Now I will show you how to minimize this output. See at the end for your example code. Best Performance The most performant way

问题 In the code below, the variable "yourVariable" is defined in a struct. Then I use a slider to change the "yourVariable" but when I try and use the variable in the SecondView, it uses the original variable and not the updated one. I have been told I need to update the property, should I do this? If yes can someone please explain why. import SwiftUI import PlaygroundSupport struct MyVariables { static var yourVariable = 500000.0 } struct SecondView : View { @Environment(\.presentationMode) var

问题 In the code below, the variable "yourVariable" is defined in a struct. Then I use a slider to change the "yourVariable" but when I try and use the variable in the SecondView, it uses the original variable and not the updated one. I have been told I need to update the property, should I do this? If yes can someone please explain why. import SwiftUI import PlaygroundSupport struct MyVariables { static var yourVariable = 500000.0 } struct SecondView : View { @Environment(\.presentationMode) var

问题 When I try and assign the output of the Toggle to an old variable it says: Binding is not convertible to bool. Is there a way to fix this. I am coding this in Swift Playgrounds. The code below is the part which doesn't function import SwiftUI import PlaygroundSupport struct ContentView : View { @State private var redButton = false @State private var step = 0 @State private var washingHandsToggle = true @State private var wearingMaskToggle = true @State private var coverMouthToggle = true

问题 I know that to program in STDIN and STDOUT, we need to make an command line project in Xcode. But how do I take a standard input in playground. Whenever I try to run such code in playground var input = readLine()! I always get this error Execution was interrupted, reason: EXC_BAD_INSTRUCTION (Code=EXC_l386_INVOP, subcode=0x0) Is it possible to take STDIN in playground or not? UPDATE I know this error is because of nil input variable but want to know how to overcome this nil value. 回答1: Fixed

问题 I know that to program in STDIN and STDOUT, we need to make an command line project in Xcode. But how do I take a standard input in playground. Whenever I try to run such code in playground var input = readLine()! I always get this error Execution was interrupted, reason: EXC_BAD_INSTRUCTION (Code=EXC_l386_INVOP, subcode=0x0) Is it possible to take STDIN in playground or not? UPDATE I know this error is because of nil input variable but want to know how to overcome this nil value. 回答1: Fixed

问题 I know that to program in STDIN and STDOUT, we need to make an command line project in Xcode. But how do I take a standard input in playground. Whenever I try to run such code in playground var input = readLine()! I always get this error Execution was interrupted, reason: EXC_BAD_INSTRUCTION (Code=EXC_l386_INVOP, subcode=0x0) Is it possible to take STDIN in playground or not? UPDATE I know this error is because of nil input variable but want to know how to overcome this nil value. 回答1: Fixed

问题 I was trying to use auto layout in a Playground on Xcode 8. However, as soon as I added the line, I started receiving this error: Playground execution failed: error: Couldn't lookup symbols: __TWPCSo6UIView17PlaygroundSupport22PlaygroundLiveViewableS0_ __swift_FORCE_LOAD_$_swiftCoreGraphics __swift_FORCE_LOAD_$_swiftDarwin __TMaC17PlaygroundSupport14PlaygroundPage __swift_FORCE_LOAD_$_swiftObjectiveC __swift_FORCE_LOAD_$_swiftUIKit _playground_log_hidden _playground_logger_initialize __swift