Hi everyone :slightly_smiling_face: Playing with t...

# kotlinx-datetime

[Jérémy CROS]

Hi everyone 🙂
Playing with the lib, trying some very basic formatting:

val formattedArrival = arrival
    .toLocalDateTime(TimeZone.currentSystemDefault())
    .format(LocalDateTime.Format { byUnicodePattern("HH:mm") })

We're fine with hardcoded "HH:mm" for now.
But there's a warning which I don't understand : `Using format strings is discouraged. If the format string is a constant, the corresponding builder-style Kotlin code can be obtained by calling DateTimeFormat.formatAsKotlinBuilderDsl on the resulting format.`
They only way I've been able to use the mentionned DSL is that:

val format = LocalDateTime.Format { byUnicodePattern("hh:mm") }
val test = DateTimeFormat.formatAsKotlinBuilderDsl(format)

But 1) the warning is still there 2) that doesn't really help me understand what the warning is supposed to mean.
Any help? 🙂

[Dmitry Khalanskiy [JB]]

The warning wants you to print DateTimeFormat.formatAsKotlinBuilderDsl(format) and copy-paste the result into your code.

import kotlinx.datetime.*
import kotlinx.datetime.format.*

fun main() {
    val format = LocalDateTime.Format { byUnicodePattern("HH:mm") }
	println(DateTimeFormat.formatAsKotlinBuilderDsl(format))
}

prints

hour()
char(':')
minute()

so your code becomes

LocalDateTime.Format { hour(); char(':'); minute() }

[Jérémy CROS]

oooooohhhhhhhhh
Ok I get it, makes sense
(even though I would never have guessed without help 😅)
Thank you! 🙏

[Dmitry Khalanskiy [JB]]

Do you maybe have some suggestions as to which wording would be less confusing?

[Jérémy CROS]

I've been thinking about that but it's kinda hard now that I understand what the suggestion means haha 😅 Like "the wording's fine, wth was I having an issue with it?" 😅 Human brain...
I guess having the sample code with the println somewhere in the documentation would have instantly solved it for me 🙂

[Oliver.O]

This seems hard to express in abstract wording. So what about:

Using format strings like "HH:mm" is discouraged. Please see <DOC REFERENCE>.

With <DOC REFERENCE> stating:

Consider using the DSL instead of a format string like "HH:mm".
The following example prints the corresponding DSL invocations for a given format string constant:

import kotlinx.datetime.*
import kotlinx.datetime.format.*

fun main() {
    val format = LocalDateTime.Format { byUnicodePattern("HH:mm") }
	println(DateTimeFormat.formatAsKotlinBuilderDsl(format))
}

The output will be:

hour()
char(':')
minute()

You can use this to replace byUnicodePattern("HH:mm").