使用{... in}的Swift闭包语法 [英] Swift closure syntax using { ... in }

问题描述

在 Apple SwiftUI教程:绘制路径和形状，显示以下语法:

struct Badge: View {
    var body: some View {
        GeometryReader { geometry in
            Path { path in
            ...
            }
            .fill(Color.black)
        }
    }
}

我没有在结构上的Swift文档中看到语法，并感到非常困惑.

I did not see the syntax in the Swift docs on structs and feel very confused.

此外，怎么可能会知道 geometry 是在 GeometryReader 语句中，无论意味着什么?

Additionally, how might one know that geometry is "in" the GeometryReader statement, whatever that means?

推荐答案

这是尾随闭包的简化语法，所以

This is simplified syntax of trailing closure, so

Path { path in
...
}

与

Path( { (path) in
...
})

所使用的 Path 构造函数

/// Initializes to an empty path then calls `callback` to add
/// the initial elements.
public init(_ callback: (inout Path) -> ())

顺便说一句，此语法已在SwiftUI中广泛使用，因此您会在 VStack {..} ， GeometryReader {g in ...} ， ScrollView {...} 以及SwfitUI框架的几乎所有其他UI元素.

By the way, this syntax is widely used in SwiftUI, so you will see the same in VStack { .. }, GeometryReader { g in ... }, ScrollView { ... } and almost all others UI elements of SwfitUI framework.

这篇关于使用{... in}的Swift闭包语法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！