Dealing with one field that is sometimes boolean and sometimes int - moshi

Question

I'm trying to work with the reddit JSON API. There are post data objects that contain a field called edited which may contain a boolean false if the post hasn't been edited, or a timestamp int if the post was edited.
Sometimes a boolean:
{
"edited": false,
"title": "Title 1"
}
Sometimes an int:
{
"edited": 1234567890,
"title": "Title 2"
}
When trying to parse the JSON where the POJO has the field set to int, I get an error: JsonDataException: Expected an int but was BOOLEAN...
How can I deal with this using Moshi?

Answer 1

I also ran into a similar problem where I had fields that were sometimes booleans, and sometimes ints. I wanted them to always be ints. Here's how I solved it with Moshi and kotlin:
Make a new annotation that you will use on fields to should convert from boolean to int
#JsonQualifier
#Retention(AnnotationRetention.RUNTIME)
#Target(AnnotationTarget.FIELD, AnnotationTarget.VALUE_PARAMETER, AnnotationTarget.FUNCTION)
annotation class ForceToInt
internal class ForceToIntJsonAdapter {
#ToJson
fun toJson(#ForceToInt i: Int): Int {
return i
}
#FromJson
#ForceToInt
fun fromJson(reader: JsonReader): Int {
return when (reader.peek()) {
JsonReader.Token.NUMBER -> reader.nextInt()
JsonReader.Token.BOOLEAN -> if (reader.nextBoolean()) 1 else 0
else -> {
reader.skipValue() // or throw
0
}
}
}
}
Use this annotation on the fields that you want to force to int:
#JsonClass(generateAdapter = true)
data class Discovery(
#Json(name = "id") val id: String = -1,
#ForceToInt #Json(name = "thanked") val thanked: Int = 0
)

Answer 2

The easy way might be to make your Java edited field an Object type.
The better way for performance, error catching, and appliaction usage is to use a custom JsonAdapter.
Example (edit as needed):
public final class Foo {
public final boolean edited;
public final int editedNumber;
public final String title;
public static final Object JSON_ADAPTER = new Object() {
final JsonReader.Options options = JsonReader.Options.of("edited", "title");
#FromJson Foo fromJson(JsonReader reader) throws IOException {
reader.beginObject();
boolean edited = true;
int editedNumber = -1;
String title = "";
while (reader.hasNext()) {
switch (reader.selectName(options)) {
case 0:
if (reader.peek() == JsonReader.Token.BOOLEAN) {
edited = reader.nextBoolean();
} else {
editedNumber = reader.nextInt();
}
break;
case 1:
title = reader.nextString();
break;
case -1:
reader.nextName();
reader.skipValue();
default:
throw new AssertionError();
}
}
reader.endObject();
return new Foo(edited, editedNumber, title);
}
#ToJson void toJson(JsonWriter writer, Foo value) throws IOException {
writer.beginObject();
writer.name("edited");
if (value.edited) {
writer.value(value.editedNumber);
} else {
writer.value(false);
}
writer.name("title");
writer.value(value.title);
writer.endObject();
}
};
Foo(boolean edited, int editedNumber, String title) {
this.edited = edited;
this.editedNumber = editedNumber;
this.title = title;
}
}
Don't forget to register the adapter on your Moshi instance.
Moshi moshi = new Moshi.Builder().add(Foo.JSON_ADAPTER).build();
JsonAdapter<Foo> fooAdapter = moshi.adapter(Foo.class);