Auto apply buildConfigFields

apply-config.gradle

ext.applyBuildConfigFields = { def variant, Map<String, Map<String, Object>> configs ->
  def flavor = variant.productFlavors.get(0).name
  configs.each { key, entries ->
    def name = key.toUpperCase()
    def entry = entries.find { it.key == flavor }
    if (entry == null) throw new InvalidUserDataException("$key doesn't have $flavor value")

    if (entry.value instanceof String) {
      variant.buildConfigField(entry.value.class.name, name, "\"$entry.value\"")
    } else {
      variant.buildConfigField(entry.value.class.name, name, "$entry.value")
    }
  }
}

ext {
  configs = [
      test_string: [
          mock: "1",
          develop: "2",
          staging: "3",
          production: "4"
      ],
      [
      test_integer: [
          mock: 1,
          develop: 2,
          staging: 3,
          production: 4
      ]
  ]
}

android {
  applicationVariants.all { variant ->
    applyBuildConfigFields(variant, configs)
  }
}

// generate below...
// class BuildConfig {
//   public static final String TEST_STRING = "1";
//   public static final Integer TEST_INTEGER = 1;
// }