Support default values

[Anatolii Afanasev]

data class Entity(val id: Int = 42)

[Devezin]

Progress?

[Anatolii Afanasev]

@dri94 WIP

[Devezin]

when doing it, will the ability for values in json that come down as null be mapped to default values too?

[ZSpirytus]

Hello, @aafanasev

Can we provide an annotation, suppose it is called @Default, and the function annotated by it can provide the default value of this data class？

For example, for this data class:

data class Foo(
    @SerializedName("str")
    val stringValue: String,
    @SerializedName("integer")
    val intValue: Int
) {
    companion object {
        @Default
        fun provideDefault(): Foo = Foo("string value", 233)
    }
}

or data class with default value:

data class Bar(
    @SerializedName("str")
    val stringValue: String = "default",
    @SerializedName("integer") = 233
    val intValue: Int
) {
    companion object {
        @Default
        fun provideDefault(): Bar {
            return  Bar()
        }
    }
}

And then, the generated class's deserialize function will look like this:

override fun read(reader: JsonReader): Foo? {
  if (reader.peek() == JsonToken.NULL) {
    reader.nextNull()
    return null
  }

  // Foo.provideDefault() is annotated by @Default
  val default = Foo.provideDefault()

  var stringValue: kotlin.String? = null
  var intValue: kotlin.Int? = null
  reader.beginObject()
  while (reader.hasNext()) {
    if (reader.peek() == JsonToken.NULL) {
      reader.nextNull()
      continue
    }
    when (reader.nextName()) {
      "str" -> stringValue = string_adapter.read(reader)
      "integer" -> intValue = int_adapter.read(reader)
      else -> reader.skipValue()
    }
  }
  reader.endObject()

  return Foo(
      stringValue = stringValue ?: default.stringValue,
      intValue = intValue ?: default.intValue
  )
}

From the point of caller, this way just add an optional annotation, I think it just ok.

[Anatolii Afanasev]

@zkw012300 awesome! I'll prepare a POC of your solution.