Moshi/Kotlin - How to serialize NULL JSON strings into empty strings instead?

Question

I\'m trying to write a null-safe String adapter that will serialize this JSON {\"nullString\": null} into this: Model(nullString = \"\") so that any JS

Answer 1

The immediate problem is the missing reader.nextNull() call to consume the null value.

There are a couple other cleanup things you can do here, too. With @FromJson, implementing JsonAdapter is unnecessary. Also, the JsonReader and JsonWriter are not nullable.

object NULL_TO_EMPTY_STRING_ADAPTER {
  @FromJson fun fromJson(reader: JsonReader): String {
    if (reader.peek() != JsonReader.Token.NULL) {
      return reader.nextString()
    }
    reader.nextNull()
    return ""
  }
}

and use add the adapter:

val moshi = Moshi.Builder()
    .add(NULL_TO_EMPTY_STRING_ADAPTER)
    .add(KotlinJsonAdapterFactory())
    .build()