A testable RxSwift wrapper around MultipeerConnectivity

RxMultipeer is a RxSwift wrapper for MultipeerConnectivity.

Using the adapter pattern, we can test multipeer code with heavy mocking. In effect, we are trying to isolate all the untestable bits of MultipeerConnectivity into one library.

This library also gives you the flexibility to swap out the underlying mechanics of p2p with some other protocol such as websockets. At the moment it only comes with support for Apple's MultipeerConnectivity, however you can easily write your own adapters for different protocols.

Installation

Carthage

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github "RxSwiftCommunity/RxMultipeer" ~> 3.0

Example code

For a working example check out the RxMultipeer Example folder.

Advertise and accept nearby peers

import RxSwift
import RxCocoa
import RxMultipeer

let disposeBag: DisposeBag
let acceptButton: UIButton
let client: CurrentClient<MCPeerID>

client.startAdvertising()
let connectionRequests = client.incomingConnections().shareReplay(1)

acceptButton.rx_tap
  .withLatestFrom(connectionRequests)
  .subscribe(onNext: { (peer, context, respond) in respond(true) })
  .addDisposableTo(disposeBag)

client.incomingCertificateVerifications()
    .subscribe(onNext: { (peer, certificateChain, respond) in
      // Validate the certificateChain
      respond(true)
    })
    .addDisposableTo(disposeBag)

Browse for and connect to peers

import RxSwift
import RxMultipeer

let disposeBag: DisposeBag
let client: CurrentClient<MCPeerID>

client.startBrowsing()

let nearbyPeers = client.nearbyPeers().shareReplay(1)

// Attempt to connect to all peers
nearbyPeers
  .map { (peers: [Client<MCPeerID>]) in
    peers.map { client.connect(toPeer: $0, context: ["Hello": "there"], timeout: 12) }.zip()
  }
  .subscribe()
  .addDisposableTo(disposeBag)

Sending and receiving strings

Sending them:

import RxSwift
import RxCocoa
import RxMultipeer

let disposeBag: DisposeBag
let client: CurrentClient<MCPeerID>
let peer: Observable<Client<MCPeerID>>
let sendButton: UIButton

sendButton.rx_tap
  .withLatestFrom(peer)
  .map { client.send(toPeer: peer, string: "Hello!") }
  .switchLatest()
  .subscribe(onNext: { _ in print("Message sent") })
  .addDisposableTo(disposeBag)

And receiving them:

import RxSwift
import RxMultipeer

let disposeBag: DisposeBag
let client: CurrentClient<MCPeerID>

client.receive()
.subscribe(onNext: { (peer: Client<MCPeerID>, message: String) in
  print("got message \(message), from peer \(peer)")
})
.addDisposableTo(disposeBag)

Establishing a data stream

RxSwift makes sending streaming data to a persistent connection with another peer very intuitive.

The sender:

import RxSwift
import RxMultipeer

let disposeBag: DisposeBag
let client: CurrentClient<MCPeerID>
let peer: Observable<Client<MCPeerID>>
let queuedMessages: Observable<[UInt8]>

let pipe = peer.map { client.send(toPeer: peer, streamName: "data.stream") }
pipe.withLatestFrom(queuedMessages) { $0 }
  .subscribe(onNext: { (sender, message) in sender(message) })
  .addDisposableTo(disposeBag)

The receiver:

import RxSwift
import RxMultipeer

let disposeBag: DisposeBag
let client: CurrentClient<MCPeerID>
let peer: Observable<Client<MCPeerID>>

let incomingData = client.receive(fromPeer: peer, streamName: "data.stream").shareReplay(1)
incomingData
  .subscribe(onNext: { (data) in print(data) })
  .addDisposableTo(disposeBag)

Usage

Imports

import RxSwift
import RxMultipeer

Make a new build configuration for testing

Your project comes with Debug and Release build configurations by default, we need to make a new one called Testing. Please check here for step-by-step instructions.

Setting up the client

// See the link above,
// You'll need to define a new build configuration and give it the `TESTING` flag
let name = UIDevice.currentDevice().name
#if TESTING
typealias I = MockIden
let client = CurrentClient(session: MockSession(name: name))
#else
typealias I = MCPeerID
let client = CurrentClient(session: MultipeerConnectivitySession(
                 displayName: name,
                 serviceType: "multipeerex",
                 idenCacheKey: "com.rxmultipeer.example.mcpeerid",
                 encryptionPreference: .None))
#endif

Supported transfer resource types

String

func send(toPeer: Client, string: String, mode: MCSessionSendDataMode = .Reliable) -> Observable<()>
func receive() -> Observable<(Client, String)>

Data

func send(toPeer: Client, data: Data, mode: MCSessionSendDataMode = .Reliable) -> Observable<()>
func receive() -> Observable<(Client, Data)>

JSON

func send(toPeer: Client, json: [String: Any], mode: MCSessionSendDataMode = .Reliable) -> Observable<()>
func receive() -> Observable<(Client, [String: Any])>

NSURL

func send(toPeer: Client, name: String, url: NSURL, mode: MCSessionSendDataMode = .Reliable) -> Observable<NSProgress>
func receive() -> Observable<(Client, String, ResourceState)>

NSStream

func send(toPeer: Client, streamName: String, runLoop: NSRunLoop = NSRunLoop.mainRunLoop()) -> Observable<([UInt8]) -> Void>
func receive(fromPeer: Client, streamName: String, runLoop: NSRunLoop = NSRunLoop.mainRunLoop(), maxLength: Int = 512) -> Observable<[UInt8]>

Testing

When testing, use preprocesser macros to ensure that your code uses a MockSession instance instead of MultipeerConnectivitySession one. In order to achieve this you need to use preprocessor flags and swap out anywhere that references Client<T> (because T will be different depending on whether you are testing or not.) First you will need to set up a new build configuration, and then you can use preprocessor macros like so:

let name = UIDevice.currentDevice().name
#if TESTING
typealias I = MockIden
let client = CurrentClient(session: MockSession(name: name))
#else
typealias I = MCPeerID
let client = CurrentClient(session: MultipeerConnectivitySession(
                 displayName: name,
                 serviceType: "multipeerex",
                 idenCacheKey: "com.rxmultipeer.example.mcpeerid",
                 encryptionPreference: .None))
#endif

Don't worry, you should only really need preprocessor macros in one centralized place, the type of your client can be inferred by the compiler thereafter.

Mocking other nearby peers in the test environment then becomes as simple as creating other CurrentClient(session: MockSession(name: "other")). For example, if your app is running in a testing environment the following code will mock a nearby client:

let disposeBag: DisposeBag
let otherclient = CurrentClient(session: MockSession(name: "mockedother"))

// Accept all connections
otherclient.startAdvertising()

otherclient.incomingConnections()
  .subscribeNext { (client, context, respond) in respond(true) }
  .addDisposableTo(disposeBag)

// Starting from version 3.0.0 the following handler needs to be implemented
// for this library to work:
otherclient.incomingCertificateVerifications()
  .subscribeNext { (client, certificateChain, respond) in respond(true) }
  .addDisposableTo(disposeBag)

// Respond to all messages with 'Roger'
otherclient.receive()
  .map { (client: Client<MockIden>, string: String) in otherclient.send(toPeer: client, "Roger") }
  .concat()
  .subscribeNext { _ in print("Response sent") }
  .addDisposableTo(disposeBag)

Breaking changes

Version 3.0.0

Starting from version 3.0.0, incomingCertificateVerifications() -> Observable<(MCPeerID, [Any]?, (Bool) -> Void)> was introduced. This needs to be implemented in order for mock and real connections to work. Behaviour prior to this update can be reproduced by simply accepting all certificates:

let client: CurrentClient<MCPeerID
client.incomingCertificateVerifications()
    .subscribe(onNext: { (peer, certificateChain, respond) in
      // Validate the certificateChain
      respond(true)
    })
    .addDisposableTo(disposeBag)

Contributing

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RxSwiftCommunity / RxMultipeer

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