Gson Extension Functions

GsonExtensions.kt

package com.vinaysshenoy

import com.google.gson.stream.JsonReader
import com.google.gson.stream.JsonToken.NULL

inline fun JsonReader.parseObject(keys: Set<String>, block: JsonReader.(String) -> Unit) {
  beginObject()
  while (hasNext()) {
    val key = nextName()
    if (key in keys) {
      this.block(key)
    } else {
      skipValue()
    }
  }
  endObject()
}

@JvmOverloads
inline fun <R> JsonReader.parseArray(block: JsonReader.() -> R, limit: Int = 0): List<R> {
  val r = mutableListOf<R>()
  var readCount = 0
  beginArray()
  while (hasNext()) {
    if (limit > 0 && limit == readCount) {
      skipValue()
      continue
    }
    r.add(this.block())
    readCount++
  }
  endArray()
  return r
}

@JvmOverloads
inline fun <R> JsonReader.nullableGet(block: JsonReader.() -> R, ifNull: R? = null): R? {
  return when (peek()) {
    NULL -> {
      skipValue()
      ifNull
    }
    else -> this.block()
  }
}