SwiftUI Academy · 课时

使用 Stepper 递增和递减

使用步进器上下调整数值。

使用 Stepper 递增和递减 是 CoddyKit 上的免费 SwiftUI Academy 课时。这是第 3 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 SwiftUI Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 SwiftUI Academy 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Meet the Stepper

A Stepper shows minus and plus buttons to nudge a value up or down. It is ideal for quantities like item counts. ➕

Stepper Holds a Number

Like Slider, a Stepper edits a number. Tapping plus increases it and tapping minus decreases it by one step.

@State private var count = 1

Bind to State

Connect the value with the dollar sign binding and give it a label. SwiftUI handles the plus and minus taps for you.

Stepper("Quantity", value: $count)

Set a Range

Pass an in range to clamp the value. The buttons disable automatically when you hit the minimum or maximum.

Stepper("Count", value: $count, in: 0...10)

Choose the Step Size

Add a step to change how much each tap moves the value, like jumping by five instead of one.

Stepper("Score", value: $count, in: 0...100, step: 5)

Show the Value

You usually want to display the current number. Interpolate it into the label so users see the count update.

Stepper("Items: \(count)", value: $count)

Custom Increment Actions

Need full control? Use the onIncrement and onDecrement closures to run your own logic on each tap.

Stepper("Adjust") {
    count += 2
} onDecrement: {
    count -= 2
}

Stepper in a Form

Drop a Stepper into a Form row for a tidy settings look, the same way Toggle and Slider fit there.

Form {
    Stepper("Servings", value: $count)
}

A Richer Label

The label can be any view via the closure form, so you can pair text with an icon for clarity.

Stepper(value: $count) {
    Label("Cups", systemImage: "cup.and.saucer")
}

React to Changes

Other views update automatically when the count changes. Here a Text repeats based on the value.

Text(String(repeating: "⭐️", count: count))

The Full View

Everything together: a clamped Stepper with a step plus a label that shows the live count.

struct CartView: View {
    @State private var count = 1
    var body: some View {
        Stepper("Qty: \(count)", value: $count, in: 1...9)
    }
}

Quick Check

What happens when a Stepper value reaches the top of its range?

Recap

A Stepper nudges a number with plus and minus, supports an in range and step, and clamps at the edges. ➕➖

常见问题解答

「使用 Stepper 递增和递减」课时是免费的吗？

是的 — 「使用 Stepper 递增和递减」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 SwiftUI Academy 课程的其余内容，请升级到 CoddyKit PRO。 SwiftUI Academy 课程共包含 4 节课。

「使用 Stepper 递增和递减」这节课中我会学到什么？

使用步进器上下调整数值。你通过在浏览器中直接运行的动手代码来练习 SwiftUI Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 SwiftUI Academy 需要有经验吗？

无需任何先前经验。CoddyKit 上的 SwiftUI Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 3 节课，共 4 节。

「使用 Stepper 递增和递减」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 SwiftUI Academy 课中编写并运行代码吗？

能。每节 SwiftUI Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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