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SwiftUI-State和Binding - 宋明的博客
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<h1 class="title">
SwiftUI-State和Binding
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<a href="http://apolla.cc">宋明</a>
<span style="color: #ccc;">|</span>
<span class="date"><i class="fa fa-calendar-check-o" aria-hidden="true"></i> 2023/03/18</span>
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<h2><a id="state" class="anchor" aria-hidden="true"><span class="octicon octicon-link"></span></a>@State</h2>
<p><code>@State private var isPlaying = false</code><br />
在前面的文章我已用过@State属性,使用@State修饰某个属性后，SwiftUI将会把该属性存储到一个特殊的内存区域内，并且这个区域和View struct是隔离的；<br />
当@State修饰的属性的值发生变化后，SwiftUI会根据该属性重新绘制视图；<br />
举个例子：</p>
<pre class="line-numbers"><code class="language-swift">struct ContentView: View {
@State var buttonTaped = false
var body: some View {
VStack{
Button {
self.buttonTaped.toggle()
} label: {
Text(buttonTaped ? "你好" : "Hello World")
}
Button {
self.buttonTaped.toggle()
} label: {
Text(buttonTaped ? "你好" : "Hello World")
}
Button {
self.buttonTaped.toggle()
} label: {
Text(buttonTaped ? "你好" : "Hello World")
}
Button {
self.buttonTaped.toggle()
} label: {
Text(buttonTaped ? "你好" : "Hello World")
}
}
//渲染颜色
.tint(.purple)
// 按钮样式 .bordered、.borderless 和 .plain
.buttonStyle(.bordered)
//按钮边框样式
.buttonBorderShape(.capsule)
//按钮预设大小
.controlSize(.large)
}
}
</code></pre>
<p>实现效果 当我们点击时 按钮的文字会自动变化 不需要手动设置数据刷新UI<br />
<img src="media/16791176889220/16791179446238.gif" alt="2023-03-03_13-28-59 (1).gif" /></p>
<blockquote>
</blockquote>
<h2><a id="binding" class="anchor" aria-hidden="true"><span class="octicon octicon-link"></span></a>@Binding</h2>
<p>开发中，我们需要把一个View的属性，传递到一个子View中；<br />
Swift中，值传递的形式是值传递，也就是说，传个子View的是值的拷贝；子视图对这个值进行了修改后，不会影响父视图；<br />
使用@Binding修饰后，属性就变成了一个引用类型，这样子视图对值进行了修改后，父视图中的值也会发生变化</p>
<pre class="line-numbers"><code class="language-swift">struct customButton:View {
@Binding var tapCount:Int
var body: some View {
Button {
self.tapCount += 1
} label: {
Text("Hello World 第\(tapCount)次点击")
} //渲染颜色
.tint(.purple)
// 按钮样式 .bordered、.borderless 和 .plain
.buttonStyle(.bordered)
//按钮边框样式
.buttonBorderShape(.capsule)
//按钮预设大小
.controlSize(.large)
}
}
struct ContentView: View {
@State private var tapCount = 0
var body: some View {
VStack{
customButton(tapCount: $tapCount)
}
}
}
</code></pre>
<p>如果有多个按钮需要分别管理 还是推荐@State</p>
<blockquote>
<p>给每个按钮绑定自己的tapCount 属性</p>
</blockquote>
<pre class="line-numbers"><code class="language-swift">struct customButton:View {
@State var tapCount:Int = 0
var body: some View {
Button {
self.tapCount += 1
} label: {
Text("Hello World 第\(tapCount)次点击")
} //渲染颜色
.tint(.purple)
// 按钮样式 .bordered、.borderless 和 .plain
.buttonStyle(.bordered)
//按钮边框样式
.buttonBorderShape(.capsule)
//按钮预设大小
.controlSize(.large)
}
}
struct ContentView: View {
var body: some View {
VStack{
customButton()
customButton()
customButton()
}
}
}
</code></pre>
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