Scala动态变量注入实现字符串插值：如何为含不同变量的字符串序列批量替换值？

Got it, let's solve this problem of injecting values into your string placeholders. You've got strings with $Y, $m, $d placeholders, and you need to replace them with actual values dynamically. Here are two practical approaches that work perfectly for your use case:

Approach 1: Simple Chain of replace Calls #

This is the most straightforward method, great for when you have a small, fixed set of placeholders. It works seamlessly even if some strings don't include all placeholders (like your s2 missing $d).

First, define your target values (we'll use current date as an example, but you can substitute any custom values):

import java.time.LocalDate

val today = LocalDate.now()
val year = today.getYear.toString
val month = f"${today.getMonthValue}%02d" // Ensures two-digit format (e.g., "09" instead of "9")
val day = f"${today.getDayOfMonth}%02d"

Then apply the replacements to each string in your sequence:

val myStringsUpdated: Seq[String] = myStrings.map { s =>
  s.replace("$Y", year)
    .replace("$m", month)
    .replace("$d", day)
}

Approach 2: Regex + Mapping (More Flexible) #

If you anticipate adding more placeholders later, this method scales better. We'll use a regex to match any placeholder and a map to look up their corresponding values.

First, set up your placeholder-to-value mapping:

import java.time.LocalDate

val today = LocalDate.now()
val placeholderValues = Map(
  "$Y" -> today.getYear.toString,
  "$m" -> f"${today.getMonthValue}%02d",
  "$d" -> f"${today.getDayOfMonth}%02d"
)

Next, create a regex that matches any of the placeholders, then use it to replace all matches in each string:

val placeholderRegex = placeholderValues.keys.mkString("(", "|", ")").r

val myStringsUpdated: Seq[String] = myStrings.map { s =>
  placeholderRegex.replaceAllIn(s, matchResult => placeholderValues(matchResult.group(0)))
}

Key Notes #

• Both methods handle strings that don't include all placeholders (like s2) without extra code—missing placeholders simply remain untouched (which is exactly what you want).
• If you don't need current date values, just swap out the placeholderValues map with your custom values (e.g., Map("$Y" -> "2023", "$m" -> "12", "$d" -> "31")).

内容的提问来源于stack exchange，提问作者Dariusz Krynicki