GTFS Realtime¶

The GTFS Realtime module implements the General Transit Feed Specification (GTFS) Realtime for Kotlin Multiplatform.

GTFS Realtime is a standardized data feed for real-time transit information such as trip updates, vehicle positions, and service alerts. It uses Protocol Buffers as its wire format.

Features¶

Protobuf encoding and decoding with kotlinx-serialization
HTTP client for fetching feeds using Ktor
Strong type safety with Kotlin data classes and enums
Kotlin Multiplatform support (JVM, Native, JS, WASM)

Installation¶

Add the dependency to your build.gradle.kts. The client functionality requires Ktor, so also add a Ktor engine:

dependencies {
    implementation("dev.sargunv.mobility-data:gtfs-realtime:0.5.0")
    implementation("io.ktor:ktor-client-cio:3.5.2") // or another engine
}

Example¶

GtfsRealtimeClient().use { gtfsRt -> // (1)!
  val feed =
    gtfsRt
      .getFeedMessage( // (2)!
        feedUrl = "https://gtfsr.tri-rail.com/download.aspx?file=trip_updates.pb"
      )
      .getOrThrow()

  val tripUpdates = feed.entity.count { it.tripUpdate != null } // (3)!
  val vehiclePositions = feed.entity.count { it.vehicle != null }
  val alerts = feed.entity.count { it.alert != null }

  println("Trip updates: $tripUpdates")
  println("Vehicle positions: $vehiclePositions")
  println("Alerts: $alerts")
}

Create a GTFS Realtime client instance. The client implements AutoCloseable so it can be used with .use to ensure proper cleanup.
Fetch and decode a GTFS Realtime protobuf feed from a URL.
Inspect the feed entities for trip updates, vehicle positions, and alerts.

API Reference¶

See the API Reference.