doc: Modify Swift && SwiftUI (#852)
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@ -11,7 +11,7 @@ Swift 备忘清单
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```swift
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var score = 0 // 变量
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let pi = 3.14 // 常数
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let pi = 3.14 // 常量
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var greeting = "Hello"
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var numberOfToys = 8
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@ -169,7 +169,7 @@ numberOfToys += 1
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print(numberOfToys) // 打印“9”
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```
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### 常数
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### 常量声明
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常量用 `let` 声明：
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@ -187,7 +187,7 @@ let numberOfToys: Int = 8
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let isMorning: Bool = true
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```
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常量是不可变的。它们的值不能改变：
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常量 `let` 一旦设定，在程序运行时就无法改变其值:
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```swift
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let numberOfToys: Int = 8
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@ -195,7 +195,7 @@ numberOfToys += 1
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// ❌ 错误：numberOfToys 不可变
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```
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### 计算变量（get 和 set）
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### 计算属性（get 和 set）
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<!--rehype:wrap-class=row-span-3-->
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```swift
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@ -581,6 +581,8 @@ for char in "supercalifragilistice" {
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// 打印: r
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```
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`break` 关键字中断当前循环
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### 使用下划线
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```swift
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117
docs/swiftui.md
117
docs/swiftui.md
@ -233,23 +233,9 @@ Map(coordinateRegion: $region,
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Layout(布局)
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----
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### Background
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将图像用作背景
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```swift
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Text("Hello World")
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.font(.largeTitle)
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.background(
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Image("hello_world")
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.resizable()
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.frame(width: 100, height: 100)
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)
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```
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### VStack
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以垂直线排列其子项的视图
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`VStack`是 `垂直` 堆栈布局，用于将子视图垂直排列。默认将子视图从上到下排列
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```swift
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VStack (alignment: .center, spacing: 20){
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@ -259,13 +245,11 @@ VStack (alignment: .center, spacing: 20){
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}
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```
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创建静态可滚动列表。文档 - [VStack](https://developer.apple.com/documentation/swiftui/vstack)
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文档 - [VStack](https://developer.apple.com/documentation/swiftui/vstack)
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### HStack
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将其子级排列在一条水平线上的视图。
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创建静态可滚动列表
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`HStack`是 `水平` 堆栈布局，用于将子视图水平排列。默认将子视图从左到右排列
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```swift
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HStack (alignment: .center, spacing: 20){
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@ -277,9 +261,22 @@ HStack (alignment: .center, spacing: 20){
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文档 - [HStack](https://developer.apple.com/documentation/swiftui/hstack)
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### LazyVStack
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### ZStack
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`iOS 14` 一种视图，将其子级排列在垂直增长的线中，仅在需要时创建项。
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`ZStack`是 `层叠` 堆栈布局，用于将子视图重叠在一起。按照添加的顺序从下到上排列子视图，即先添加的视图会在下面，后添加的视图会覆盖在上面
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```swift
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ZStack {
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Text("Hello")
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Text("World")
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}
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```
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文档 - [ZStack](https://developer.apple.com/documentation/swiftui/zstack)
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### 懒加载 Lazy
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`iOS 14.0` 之后新增的视图，仅在需要时才会创建和渲染
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```swift
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ScrollView {
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@ -291,58 +288,30 @@ ScrollView {
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}
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```
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文档 - [LazyVStack](https://developer.apple.com/documentation/swiftui/lazyvstack)
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- 懒加载：只有当子视图进入可视区域时，才会被创建和渲染
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- 自适应：子视图的宽高可以自适应
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- 性能优化：适用于大量子视图或动态内容的场景
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<!--rehype:className=style-round-->
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### LazyHStack
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<!--rehype:wrap-class=col-span-2-->
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将子项排列在水平增长的线中的视图，仅在需要时创建项。
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```swift
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ScrollView(.horizontal) {
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LazyHStack(alignment: .center, spacing: 20) {
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ForEach(1...100, id: \.self) {
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Text("Column \($0)")
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}
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}
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}
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```
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文档 - [LazyHStack](https://developer.apple.com/documentation/swiftui/lazyhstack)
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### ZStack
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覆盖其子项的视图，使子项在两个轴上对齐。
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```swift
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ZStack {
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Text("Hello")
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.padding(10)
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.background(Color.red)
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.opacity(0.8)
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Text("World")
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.padding(20)
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.background(Color.red)
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.offset(x: 0, y: 40)
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}
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```
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文档 - [ZStack](https://developer.apple.com/documentation/swiftui/zstack)
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- 文档 - [LazyVStack](https://developer.apple.com/documentation/swiftui/lazyvstack)
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- 文档 - [LazyHStack](https://developer.apple.com/documentation/swiftui/lazyhstack)
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### LazyVGrid
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<!--rehype:wrap-class=col-span-2-->
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容器视图，将其子视图排列在垂直增长的网格中，仅在需要时创建项目。
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容器视图，将其子视图排列在`垂直`增长的网格中，仅在需要时创建项目
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```swift
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var columns: [GridItem] = Array(repeating: .init(.fixed(20)), count: 5)
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var columns: [GridItem] =
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Array(
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repeating: .init(.fixed(20)), count: 5
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)
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ScrollView {
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LazyVGrid(columns: columns) {
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ForEach((0...100), id: \.self) {
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Text("\($0)").background(Color.pink)
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}
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LazyVGrid(columns: columns) {
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ForEach((0...100), id: \.self) {
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Text("\($0)").background(Color.pink)
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}
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}
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}
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```
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@ -350,7 +319,7 @@ ScrollView {
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### LazyHGrid
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一种容器视图，将其子视图排列在水平增长的网格中，仅在需要时创建项目。
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容器视图，将其子视图排列在`水平`增长的网格中，仅在需要时创建项目
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```swift
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var rows: [GridItem] =
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@ -360,8 +329,8 @@ var rows: [GridItem] =
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ScrollView(.horizontal) {
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LazyHGrid(rows: rows, alignment: .top) {
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ForEach((0...100), id: \.self) {
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Text("\($0)").background(Color.pink)
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ForEach((0...100), id: \.self) {
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Text("\($0)").background(Color.pink)
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}
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}
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}
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@ -397,6 +366,20 @@ HStack {
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文档 - [Divider](https://developer.apple.com/documentation/swiftui/divider)
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### Background
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将图像用作背景
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```swift
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Text("Hello World")
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.font(.largeTitle)
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.background(
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Image("hello_world")
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.resizable()
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.frame(width: 100, height: 100)
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)
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```
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Input(输入)
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---
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