RxJavaErrorHandling3.kt

class RxJavaUnitTest {

  companion object {
    private const val USER_ID = "USER_ID"
    private const val NAME = "John Doe"
    private const val AGE = 20
    private const val EMPTY = ""
  }

  @Test
  fun getUserWithGoodErrorHandling() {
    getUserId()
      .doOnNext{ println("get user") }
      .flatMap(this::getUser)
      .doOnNext{ println("done get user") }
      .doOnNext{ println("saving user") }
      .flatMap(this::saveUser)
      .doOnNext{ println("done saving user") }
      .subscribe({ user ->
        println(user)
      }, {
        println(it.message)
      })
  }

  private fun getUserId(): Observable<String> {
    return Observable.fromCallable {
      EMPTY
    }
  }

  private fun getUser(id: String): Observable<User> {
    if (id == EMPTY) {
      throw Exception("User ID is invalid")
    }
    val user = User(
      id = id,
      name = NAME,
      age =  AGE
    )
    return Observable.fromCallable { user }
  }

  private fun saveUser(user: User): Observable<User> {
    // Perform save to user
    return Observable.fromCallable { user }
  }
}

data class User(
  val id: String,
  val name: String,
  val age: Int
)