A common use-case is to derive value from other properties. In the following example, we’re creating a filename based on the name and file extension: structContent{varname:StringletfileExtension:String// A computed property to generate a filename.varfilename:String{returnname+"."+fileExtension...
If you know C or Objective-C then you might be familiar with Enums and Structs. However, if you don’t know either of those languages then you are probably wondering what is their purpose and why you should use them. In Swift, both an Enum and Struct have an extended feature set from...
SE-0438extends key paths to support static properties of types, further rounding out the power of key paths in Swift. For example, we could define a struct with one static variable and one instance variable like this: structWarpDrive{staticletmaximumSpeed=9.975varcurrentSpeed=8.0} ...
Using the ImageDownloader class, we will define a protocol to notify conformed objects when a task is completed or failed. This protocol will have a set of rules (or functions). A class, struct, or enum can conform to the protocol and complete the implementation of these functions. In this...
For example, SE-0401 removes a feature that was introduced back in Swift 5.5: actor inference for property wrappers. Previously, any struct or class using a property wrapper with @MainActor for its wrapped value will automatically be @MainActor. This is what makes @StateObject and @Observed...
在Swift 4 中新增了一种 Key-Path 表达式,该表达式可用于 KVC & KVO 中的 APIs,格式如下: \[TypeName].[PropertyName] 示例代码如下: structSomeStructure{varsomeProperty:Int}funcsmartKeyPath() {lets=SomeStructure(someProperty:12)letkeyPath=\SomeStructure.somePropertyletvalue=s[keyPath: keyPath]print(val...
As of Swift 3, the Swift standard library defines the AnyHashable supertype. This means that types conforming to the Hashable protocol can be used as AnyHashable. In the Swift standard library, AnyHashable is defined as a struct. public struct AnyHashable { public init<H>(_ base: H) where ...
Swift 5.2 is now available as part of Xcode 11.4. In this article, you’ll get an overview of the changes you’ll see moving to Swift 5.2.
Previously, we had to create a new @main struct that had an asynchronous main() method, so this new, simpler approach is a big improvement. Opaque parameter declarations SE-0341 unlocks the ability to use some with parameter declarations in places where simpler generics were being used. As an...
Result Builder (结果生成器)是驱动 SwiftUI 声明式语法的 Swift 特性之一。在前几个版本中,Swift 编译器需要花费很长的时间来确定错误,因为类型检查器搜索了大量无效路径。 从Swift 5.8 开始,错误代码的类型检查速度将大幅度提升,对错误代码的错误信息现在也更加准确。 例如,我们来看下以下代码: 在这个代码中,核心...