格式化货币与数字
共享格式化逻辑，让两个应用中的显示都正确
格式化货币与数字 是 CoddyKit 上的免费 Kotlin Multiplatform Academy 课时。 这是第 2 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 Kotlin Multiplatform Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Kotlin Multiplatform 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。
Computing vs Displaying
Calculating a total is one job; formatting it as text is another. Keeping them separate keeps your shared code clean and reusable.
Why Format in Shared Code
If both apps show prices the same way, users trust them more. A shared formatter guarantees consistent output everywhere.
Two Decimals, Always
Money usually needs exactly two decimals. Decide that rule once so prices never show as 9.5 or 9.512 by accident. 💵
A Portable Pad Trick
You can build a price string with simple math instead of platform APIs. This pad step ensures the cents are always two digits.
fun cents(v: Double): String {
val c = (v * 100).toInt() % 100
return c.toString().padStart(2, '0')
}Assemble the Price String
Combine the whole part and the padded cents to get clean output. This format runs identically on Android and iOS.
fun money(v: Double) = (v.toInt()).toString() + "." + cents(v)Add the Currency Symbol
Prefix a symbol so the value reads as money. Pass it in rather than hardcoding, so different markets stay flexible.
fun price(v: Double, symbol: String = "$") = symbol + money(v)Thousands Separators
Big numbers are easier to read grouped, like 1,200. Put this grouping logic in shared code so both apps match.
Locale Is Tricky
Some regions use a comma for decimals. Full locale formatting often needs expect/actual to reach each platform's native formatter.
Declare a Shared Contract
Use expect to declare locale formatting in common code, then let each platform supply its real implementation.
expect fun formatLocalized(amount: Double, currency: String): StringPercentages Too
Tax rates read better as percent. A small percent helper turns 0.18 into a friendly 18% for the UI.
fun percent(rate: Double) = (rate * 100).toInt().toString() + "%"Format Last, Compute First
Always do the math on numbers, then format only at the edge. This keeps your calculations precise and testable.
Quick Check
Why keep formatting separate from calculation in shared code?
Recap: Numbers In, Strings Out
You formatted money with padded cents, symbols and percents, and reached for expect/actual when locale rules got real. ✅
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- 课程
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常见问题解答
「格式化货币与数字」课时是免费的吗？
是的 — 「格式化货币与数字」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 Kotlin Multiplatform Academy 课程的其余内容，请升级到 CoddyKit PRO。 Kotlin Multiplatform Academy 课程共包含 4 节课。
「格式化货币与数字」这节课中我会学到什么？
共享格式化逻辑，让两个应用中的显示都正确 你通过在浏览器中直接运行的动手代码来练习 Kotlin Multiplatform 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 Kotlin Multiplatform Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Kotlin Multiplatform 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 2 节课，共 4 节。
「格式化货币与数字」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 Kotlin Multiplatform Academy 课中编写并运行代码吗？
能。每节 Kotlin Multiplatform 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。