Moshi Kotlin Codegen Example with Custom Adapter

Moshi Kotlin Codegen Example with Custom Adapter

//app build.gradle
apply plugin: 'kotlin-kapt'
...

dependencies {
{
    //Moshi Core
    implementation "com.squareup.moshi:moshi:1.8.0"
    
    //Moshi Codegen
    kapt "com.squareup.moshi:moshi-kotlin-codegen:1.8.0"
}

//Movie JSON
{
    "vote_count": 2026,
    "id": 19404,
    "title": "Example Movie",
    "image_path": "/this-is-an-example-movie-image.jpg",
    "genre_ids": [
      35,
      18,
      10749
    ],
    "overview": "Overview of example movie"
}

@JsonClass(generateAdapter = true)
data class Movie (
    @Json(name = "vote_count") val voteCount: Int = -1,
    val id: Int,
    val title: String,
    @Json(name = "image_path") val imagePath: String,
    @Json(name = "genre_ids") val genres: List<Genre>,
    val overview: String
)

@JsonClass(generateAdapter = true)
data class Genre(val id: Int, val name: String)

//Movie genres from the The movie database - https://www.themoviedb.org/
class GenreAdapter  {

        @ToJson
        fun toJson(genres: List<Genre>): List<Int> {
            return genres.map { genre -> genre.id}
        }

        @FromJson
        fun fromJson(genreId: Int): Genre {

            when (genreId) {
                28 -> return Genre(28, "Action")
                12 -> return Genre(12, "Adventure")
                16 -> return Genre(16, "Animation")
                35 -> return Genre(35, "Comedy")
                80 -> return Genre(80, "Crime")
                99 -> return Genre(99, "Documentary")
                18 -> return Genre(18, "Drama")
                10751 -> return Genre(10751, "Family")
                14 -> return Genre(14, "Fantasy")
                36 -> return Genre(36, "History")
                27 -> return Genre(27, "Horror")
                10402 -> return Genre(10402, "Music")
                10749 -> return Genre(10749, "Romance")
                9648 -> return Genre(9648, "Mystery")
                878 -> return Genre(878, "Science Fiction")
                10770 -> return Genre(10770, "TV Movie")
                53 -> return Genre(53, "Mystery")
                10752 -> return Genre(10752, "War")
                37 -> return Genre(37, "Western")
                else -> throw JsonDataException("unknown genre id: $genreId")
            }
        }
    }
  
val moshi: Moshi = Moshi.Builder().add(GenreAdapter()).build()
val adapter: JsonAdapter<Movie> = moshi.adapter(Movie::class.java)
val movie = adapter.fromJson(moviesJson))