T-Spoon/EventSource

A simple Swift client library for the Server Sent Events (SSE)

EventSource

SSE Client written on Swift using NSURLSession.

Abstract

This is an EventSource implementation written on Swift trying to keep the API as similar as possible to the JavaScript one. Written following the W3C EventSource. If something is missing or not completely right open an issue and I'll work on it!

How to use it?

It works just like the JavaScript version, the main difference is when creating a new EventSource object you can add headers to the request, for example if your server uses basic auth you can add the headers there.

Last-Event-Id is completely handled by the library, so it's sent to the server if the connection drops and library needs to reconnect. Also the Last-Event-Id is stored in NSUserDefaults so we can keep the last received event for the next time the app is used to avoid receiving duplicate events.

The library automatically reconnects if connection drops. The reconnection time is 3 seconds. This time may be changed by the server sending a retry: time-in-milliseconds event.

Also in sse-server folder you will find an extremely simple node.js server to test the library. To run the server you just need to:

• npm install
• node sse.js

Install

You can just drag the EventSource.swift file to your project or using CocoaPods:

pod 'IKEventSource'

Then import the library:

import IKEventSource

Javascript API:

var eventSource = new EventSource(server);

eventSource.onopen = function() {
    // When opened
}

eventSource.onerror = function() {
    // When errors
}

eventSource.onmessage = function(e) {  
    // Here you get an event without event name!
}

eventSource.addEventListener("ping", function(e) {
  // Here you get an event 'event-name'
}, false);

eventSource.close();

Swift API:

var eventSource: EventSource = EventSource(url: server, headers: ["Authorization" : basicAuthAuthorization])
   
eventSource.onOpen {
  // When opened
}
        
eventSource.onError { (error) in
  // When errors
}

eventSource.onMessage { (id, event, data) in
  // Here you get an event without event name!
}
   
eventSource.addEventListener("event-name") { (id, event, data) in
  // Here you get an event 'event-name'
}

eventSource.close()

We added the following methods that are not available on JavaScript EventSource API but we think they might be useful:

public func removeEventListener(event: String) -> Void
public func events() -> Array<String>

Also the following properties are available:

• readyState: Status of EventSource
  • EventSourceState.Closed
  • EventSourceState.Connecting
  • EventSourceState.Open
• URL: EventSource server URL.

Examples:

---

Event:

id: event-id
event: event-name
data: event-data

Calls

eventSource.addEventListener("event-name") { (id, event, data) in
  // Here you get an event 'event-name'
}

---

Event:

id: event-id
data: event-data

data: event-data

Calls

eventSource.onMessage { (id, event, data) in
  // Here you get an event without event name!
}

---

Event:

id: event-id
data: event-data-1
data: event-data-2
data: event-data-3

Calls

eventSource.onMessage { (id, event, data) in
  // Here you get an event without event name!
  // data: event-data-1\nevent-data-2\nevent-data-3
}

---

Event:

:heartbeat

Calls

nothing it's a comment

---

Live example

This is the example shipped with the app. If you run the server and run the app you will be able to see this example live. The moving box is just to show that everything works on background and the main thread performance shows no degradation. (The gif is pretty bad to see that, but if you click on the image you will be taken to the gfycat version of the gif which runs way smoother)

Contributors

Thanks to all the contributors for pointing out missing stuff or problems and fixing them or opening issues!!

• hleinone
• chrux
• danielsht86
• Zeeker
• col
• heyzooi
• alexpalman
• robbiet480

Contact Us

If you find any bugs or have a problem while using this library, please open an issue in this repo (or a pull request :)).