Hey guys! ```fun LocalDate.toFormattedDateString()...

# multiplatform

[João Henrique de Souza Silva]

Hey guys!

fun LocalDate.toFormattedDateString(): String =
    format(LocalDate.Format {
        dayOfWeek(DayOfWeekNames.ENGLISH_ABBREVIATED)
        chars(", ")
        dayOfMonth()
        char(' ')
        monthName(MonthNames.ENGLISH_ABBREVIATED)
        char(' ')
        year()
    })

How can I make dayOfWeek and monthName be translated based on the device language? I'm using kotlinx-datetime.

[youssef hachicha]

u probably need an expect, actual function for each platform

[João Henrique de Souza Silva]

Why?

[youssef hachicha]

https://github.com/Kotlin/kotlinx-datetime/discussions/253

[youssef hachicha]

Currently, the kotlinx-datetime library does not support locale-aware formatting for date components like day names and month names. The formatting functions provided by kotlinx-datetime are locale-invariant, meaning they do not adapt to different device languages or regional settings. This limitation is acknowledged in the library's discussions, where it's noted that a good date-time formatting API should make it easy to write correct code for both machine-human and machine-machine communication, which typically involves locales.

[João Henrique de Souza Silva]

Do you have any code demonstration of how I could use the expect and actual?

[youssef hachicha]

i don't, are u familiar with the concept of expect, actual?

[youssef hachicha]

if yes then u just need to use platform-specific libraries that offer comprehensive localization support

[João Henrique de Souza Silva]

ok, thank you!

[João Henrique de Souza Silva]

I'll search how can I do this, mainly in iOS

[Lucas Prioste]

Hi @João Henrique de Souza Silva, I think this could help you.
In common main

expect fun LocalDate.formatDateToLocale(): String

In android side

actual fun LocalDate.formatDateToLocale(): String {
    val formatter = DateTimeFormatter
        .ofLocalizedDate(FormatStyle.MEDIUM)
        .withLocale(Locale.getDefault())
    return this.toJavaLocalDate().format(formatter)
}

In iOS side

actual fun LocalDate.formatDateToLocale(): String {
    val formatter = NSDateFormatter().apply {
        dateStyle = NSDateFormatterMediumStyle
        timeStyle = NSDateFormatterNoStyle
        locale = NSLocale.currentLocale
    }

    val calendar = NSCalendar.currentCalendar
    val nsDate = calendar.dateFromComponents(this.toNSDateComponents()) ?: return ""
    return formatter.stringFromDate(nsDate)
}

[João Henrique de Souza Silva]

Thank you, @Lucas Prioste, for your code. I also created another function that receives a pattern and uses expect and actual to implement it on both platforms.

enum class FormatStyle {
    FULL,
    LONG,
    MEDIUM,
    SHORT,
}

import com.my.path.FormatStyle
import kotlinx.datetime.LocalDate
import kotlinx.datetime.LocalDateTime
import kotlinx.datetime.toJavaLocalDate
import java.time.format.DateTimeFormatter
import java.util.Locale
import java.time.format.FormatStyle as FS

actual fun LocalDate.formatDateToLocale(style: FormatStyle): String {
    val style = when (style) {
        FormatStyle.FULL -> FS.FULL
        FormatStyle.LONG -> FS.LONG
        FormatStyle.MEDIUM -> FS.MEDIUM
        FormatStyle.SHORT -> FS.SHORT
    }

    val formatter = DateTimeFormatter
        .ofLocalizedDate(style)
        .withLocale(Locale.getDefault())
    return this.toJavaLocalDate().format(formatter)
}

actual fun LocalDate.formatDateToLocale(pattern: String): String {
    val formatter = DateTimeFormatter
        .ofPattern(pattern)
    return this.toJavaLocalDate().format(formatter)
}

actual fun LocalDateTime.formatDateToLocale(style: FormatStyle): String =
    date.formatDateToLocale(style)

actual fun LocalDate.formatDateToLocale(style: FormatStyle): String {
    val style = when (style) {
        FormatStyle.FULL -> NSDateFormatterFullStyle
        FormatStyle.LONG -> NSDateFormatterLongStyle
        FormatStyle.MEDIUM -> NSDateFormatterMediumStyle
        FormatStyle.SHORT -> NSDateFormatterShortStyle
    }
    val formatter = NSDateFormatter().apply {
        dateStyle = style
        timeStyle = NSDateFormatterNoStyle
        locale = NSLocale.currentLocale
    }

    val calendar = NSCalendar.currentCalendar
    val nsDate = calendar.dateFromComponents(this.toNSDateComponents()) ?: return ""
    return formatter.stringFromDate(nsDate)
}

actual fun LocalDate.formatDateToLocale(pattern: String): String {
    val formatter = NSDateFormatter().apply {
        dateFormat = pattern
        locale = NSLocale.currentLocale
    }

    val calendar = NSCalendar.currentCalendar
    val nsDate = calendar.dateFromComponents(this.toNSDateComponents()) ?: return ""
    return formatter.stringFromDate(nsDate)
}

actual fun LocalDateTime.formatDateToLocale(style: FormatStyle): String =
    date.formatDateToLocale(style)