I have a format that outputs lines of content like...

# serialization

[Zyle Moore]

I have a format that outputs lines of content like PID=1.1 I made a serializable data class to represent this

@Serializable
data class Pid(
    val first: Digits,
    val second: Digits? = null,
)

If second is absent, then the period and second number are not included.
Pid("1") == PID=1
Pid("1", "1") == PID=1.1

I'm making a hand-built custom serializer, but can't figure out how the descriptor aligns to the serialization and deserialization methods. Does second become a substructure made up of separator value ".1" Is it inline? Would it be elements[2] of the base descriptor, or closer to elements[1][1]?

[Adam S]

Personally I find it's usually easier to write a delegate class that matches the expected output format, and then convert to/from using Kotlin code.

[Adam S]

for example

Pid.kt

[Zyle Moore]

Okay, I think I understand.

The domain object Pid is Serializable. This is what the rest of the functional code is using. There's nothing special here except for with specifying which serializer to use. The twist though, is that the properties from Pid are never actually touched by the encoder.

The serializer, since it's hand built, is in control of what gets sent to the encoder. The first and second properties from Pid are never passed as a parameter to any encodeX method.

Instead, a new Serializable object, the PidDelegate is created, whose value is the entire serialized output made up of the primitive; the whole formatted string, with the expected period and second string, in a single value.

Then it's just "serialize the `PidDelegate`", and since it's just a value class for a String, what gets sent to the encoder is the plain, full, singular string value.

Did I get that right?

[Adam S]

yes, exactly!

[Zyle Moore]

Awesome, thanks so much for the guidance Adam. I was able to incorporate your changes and come up with this, which pretty gracefully handles the value class errors during deserialization as well. Still rough, but far better than I had earlier!

Here's the console output from the below
> PID=123.121
> decodedLocalPid: Pid(first=Digits(nonEmptyString=NonEmptyString(string=456)), second=null) true
> decodedSourcePid: Pid(first=Digits(nonEmptyString=NonEmptyString(string=456)), second=Digits(nonEmptyString=NonEmptyString(string=123))) true
> java.lang.IllegalArgumentException: must not be empty
> java.lang.IllegalArgumentException: must contain only ASCII digits in range 0..9

Untitled.cpp

[Adam S]

that looks great!