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README iOS (0.5.1)

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Eric Lange edited this page Nov 27, 2018 · 2 revisions

The LiquidCore Project (iOS)

LiquidCore enables Node.js virtual machines to run inside Android and iOS apps. It provides a complete runtime environment, including a virtual file system and native MySQL support.

Version

0.5.0

The framework is distributed through Carthage.

  1. Install Carthage as described here.

  2. Create a Cartfile that includes the LiquidCore framework: git "git@github.com:LiquidPlayer/LiquidCore.git" ~> 0.5.1

  3. Run carthage update. This will fetch dependencies into a Carthage/Checkouts folder, then build each one or download a pre-compiled framework.

  4. On your application targets’ General settings tab, in the “Linked Frameworks and Libraries” section, drag and drop LiquidCore.framework from the Carthage/Build folder on disk.

  5. On your application targets’ Build Phases settings tab, click the + icon and choose New Run Script Phase. Create a Run Script in which you specify your shell (ex: /bin/sh), add the following contents to the script area below the shell:

    /usr/local/bin/carthage copy-frameworks

  6. Add the paths to the framework under “Input Files":

    $(SRCROOT)/Carthage/Build/iOS/LiquidCore.framework

  7. Add the paths to the copied framework to the “Output Files”:

    $(BUILT_PRODUCTS_DIR)/$(FRAMEWORKS_FOLDER_PATH)/LiquidCore.framework

API Documentation

Version 0.5.1

Table of Contents

  1. Use Cases
  2. "Hallo, die Weld!" Micro Service Tutorial
  3. Building the LiquidCore iOS framework
  4. License

Use Cases

This section covers the two major intended use cases of LiquidCore, complete with Hello, World! step-by-step examples.

  1. The Micro Service
  2. The Micro App

The Micro Service

A micro app is built on a micro service. A micro service is nothing more than an independent Node.js instance whose startup code is referenced by a URI. For example:

Swift

import LiquidCore
...

let url = URL(string: "http://my.server.com/path/to/code.js")
let service = LCMicroService(url: url!)
service?.start()

Objective-C

#import <LiquidCore/LiquidCore.h>
...

NSURL *url = [NSURL URLWithString:@"http://my.server.com/path/to/code.js"];
LCMicroService *service = [[LCMicroService alloc] initWithURL:url];
[service start];

The service URI can either refer to a server URL or a local resource (e.g. NSURL *url = [[NSBundle mainBundle] URLForResource: @"somefile" withExtension:@"js"];). LiquidCore is designed to primarily use remote URLs, as dynamic updates are an important value proposition, but local resources are also supported.

A micro service can communicate with the host app once the Node.js environment is set up. This can be determined by specifying an LCMicroServiceDelegate in the LCMicroService constructor:

Swift

let url = URL(string: "http://my.server.com/path/to/code.js")
let service = LCMicroService(url: url!, delegate:self)
service?.start()

...
func onStart(_ service: LCMicroService!) {
    // .. The environment is live, but the startup JS code (from the URI)
    // has not been executed yet.
}

Objective-C

NSURL *url = [NSURL URLWithString:@"http://my.server.com/path/to/code.js"];
LCMicroService *service = [[LCMicroService alloc] initWithURL:url delegate:self];
[service start];

...

- (void) onStart:(LCMicroService*)service
{
    // .. The environment is live, but the startup JS code (from the URI)
    // has not been executed yet.
}

A micro service communicates with the host through a simple EventEmitter interface, eponymously called LiquidCore. For example, in your JavaScript startup code (code.js in this example):

LiquidCore.emit('my_event', {foo: "hello, world", bar: 5, l337 : ['a', 'b'] })

On the iOS side, the host app can listen for events through the LCMicroServiceEventListener protocol:

Swift

// ... in the onStart:synchronizer: method:
service.addEventListener("my_event", listener: self)

...
func onEvent(_ service: LCMicroService!, event: String!, payload: Any?) {
    var p = (payload as! Dictionary<String,AnyObject>)
    NSLog(format:"Event: %@: %@", args:event, p["foo"]);
    // logs: Event:my_event: hello, world
}

Objective-C

// ... in the onStart:synchronizer: method:
[service addEventListener:@"my_event" listener:self];

...

- (void) onEvent:(LCMicroService*)service event:(NSString*)event payload:(id _Nullable)payload
{
    NSLog(@"Event: %@: %@", event, payload[@"foo"]);
    // logs: Event:my_event: hello, world
}

Similarly, the micro service can listen for events from the host:

Swift

var payload = ["hallo" : "die Weld"]
service.emitObject("host_event", object:payload)

Objective-C

NSDictionary *payload = @{ @"hallo" : @"die Weld" };
[service emitObject:@"host_event" object:payload];

Then, in Javascript:

LiquidCore.on('host_event', function(msg) {
   console.log('Hallo, ' + msg.hallo)
})

LiquidCore creates a convenient virtual file system so that instances of micro services do not unintentionally or maliciously interfere with each other or the rest of the iOS filesystem. The file system is described in detail here.

The Micro App

Important Notice: The Micro App concept is being completely re-thought. In version 0.6.0, LiquidView will disappear from LiquidCore and be reborn in a separate project built on top of LiquidCore. The goal is to keep LiquidCore focused on just providing a fast, secure Node VM for mobile devices. The UI will reappear in a project called caraml. Stay tuned.

There are many uses for micro services. They are really useful for taking advantage of all the work that has been done by the Node community. But we want to be able to create our own native applications that do not require much, if any, interaction from the host. To achieve this, we will introduce one more term: Surface. A surface is a UI canvas for micro services.

There are two surfaces so far:

  1. ConsoleSurface. A ConsoleSurface is simply a Node.js terminal console that displays anything written to console.log() and console.error(). It also allows injection of Javascript commands, just like a standard Node console. Run the NodeConsole app under the Tests directory to see it in action.
  2. ReactNativeSurface. You can drive native UI elements using the React Native framework from within your micro app.

There are other surfaces under consideration, including:

  • WebSurface - a WebView front-end where a micro service can write to the DOM
  • CardSurface - a limited feature set suitable for driving card-like UI elements in a list
  • OpenGLSurface - an OpenGL canvas

Eventually, we would like to have virtual/augmented reality surfaces, as well as non-graphical canvases such as chat and voice query interfaces.

"Hallo, die Weld!" Micro Service Tutorial

Prerequisites

(You can find all the code below in a complete example project here if you get stuck).

To use a micro service, you need two things: the micro service code, and a host app.

We will start by creating a very simple micro service, which does nothing more than send a welcome message to the host. This will be served from a machine on our network. Start by installing the command-line interface:

$ npm install -g liquidcore-cli

Next, generate a project called helloworld using the tool:

$ liquidcore init helloworld
$ cd helloworld && npm install

This will generate a small Hello World project for you. We are going to change it a bit, but the important thing is that this sets everything up correctly and provides you with some nice features like a development server and production bundler.

Once installation has completed, edit the file index.js in your helloworld directory and replace its contents with the following:

/* Hello, World! Micro Service */

// A micro service will exit when it has nothing left to do.  So to
// avoid a premature exit, let's set an indefinite timer.  When we
// exit() later, the timer will get invalidated.
setInterval(function() {}, 1000)

// Listen for a request from the host for the 'ping' event
LiquidCore.on( 'ping', function() {
    // When we get the ping from the host, respond with "Hallo, die Weld!"
    // and then exit.
    LiquidCore.emit( 'pong', { message: 'Hallo, die Weld!' } )
    process.exit(0)
})

// Ok, we are all set up.  Let the host know we are ready to talk
LiquidCore.emit( 'ready' )

Finally, you can now run your development server.

$ npm start server

This will fire off a server built on the metro bundler. Metro does everything we need and more, so if you've used the old liquidserver in the past, this replaces that. Anyway, congratulations, you just created a micro service. You can test that it is working correctly by navigating to http://localhost:8082/liquid.bundle?platform=ios in your browser. You should be able to find the contents of index.js that you just created with some additional wrapper code. The wrapper is simply to allow multiple Node.js modules to be packed into a single file. If you were to require() some other module, that module and its dependencies would get wrapped into this single file.

You can leave that running or restart it later. Now we need to create a host app.

  1. In XCode, create a new project by selecting File->New->Project->Single View App
  2. Fill out the basics and press Next (Product Name: HelloWorld, Organization Name: LiquidPlayer, Language: Swift). Leave the rest as defaults.
  3. Select a location for it and press Create
  4. Open the ViewController.swift file and replace the code with the following contents:
import UIKit

class ViewController: UIViewController {

    var text: UILabel = UILabel()
    var button: UIButton = UIButton(type: .system)
    
    override func viewDidLoad() {
        super.viewDidLoad()

        text.textAlignment = .center
        text.text = "Hello World!"
        text.font = UIFont(name: "Menlo", size: 17)
        self.view.addSubview(text)
        
        button.setTitle("Sprechen Sie Deutsch!", for: .normal)
        button.titleLabel?.font = UIFont(name: "Menlo", size: 17)
        button.addTarget(self, action: #selector(onTouch), for: .touchUpInside)
        self.view.addSubview(button)
        
        self.text.translatesAutoresizingMaskIntoConstraints = false
        self.button.translatesAutoresizingMaskIntoConstraints = false
        
        let top = UILayoutGuide()
        let bottom = UILayoutGuide()
        self.view.addLayoutGuide(top)
        self.view.addLayoutGuide(bottom)
        
        let views = [ "text": text, "button": button, "top":top, "bottom":bottom ]
        let c1 = NSLayoutConstraint.constraints(withVisualFormat: "H:|-[text]-|", metrics: nil, views: views)
        let c2 = NSLayoutConstraint.constraints(withVisualFormat: "H:|-[button]-|", metrics: nil, views: views)
        let c3 = NSLayoutConstraint.constraints(withVisualFormat: "V:|[top]-[text]-[button]-[bottom(==top)]|",
                                                metrics: nil, views: views)
        self.view.addConstraints(c1 + c2 + c3)
    }
    
    @objc func onTouch(sender:UIButton!) {
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

}

You now have a basic app that does very little. Go ahead and run it in your simulator. You should see a white background with a message that says "Hello World!" and a button below it that says "Sprechen Sie Deutsch". This is just a simple Hello World app. We are going to teach it to speak German by using our LiquidCore micro service.

Now it is time to connect LiquidCore. First, you must add the framework. Follow the instructions at the top of the file for this. The first time you run carthage update, it will take a long time as it needs to clone the entire repo. But after the first time, it should be quicker. Everything should continue working the same. Once this is done, re-run your app. It should continue working as before.

Now, let's connect our button to the micro service. Edit ViewController.swift in our app, and replace the first couple of lines with the following:

import UIKit
import LiquidCore

class ViewController: UIViewController, LCMicroServiceDelegate, LCMicroServiceEventListener {

Make sure you change the internet address to the correct IP address or name on your network.

Now, replace the onTouch() function with the following:

    @objc func onTouch(sender:UIButton!) {
        let url = LCMicroService.devServer()
        let service = LCMicroService(url: url!, delegate: self)
        service?.start()
    }
    
    func onStart(_ service: LCMicroService!) {
        service.addEventListener("ready", listener: self)
        service.addEventListener("pong", listener: self)
    }
    
    func onEvent(_ service: LCMicroService!, event: String!, payload: Any?) {
        if event == "ready" {
            service.emit("ping")
        } else if event == "pong" {
            DispatchQueue.main.async {
                var p = (payload as! Dictionary<String,AnyObject>)
                self.text.text = p["message"] as? String
            }
        }
    }

Now, restart the app and then click the button. The "Hello World" message should change to German. You have successfully connected a micro service to a host app!

To demonstrate the instant update feature, leave the app and server running. Now, edit index.js on your server machine to respond with a different message and then save:

...
    LiquidCore.emit( 'pong', { message: 'Das ist super!' } )
...

Go back to the app and press the button again. Your message should update.

That's it. That's all there is to it. Of course, this is an overly simplified example. You have all of the capabilities of Node.js at your disposal.

A quick note about the LCMicroService.devServer(): this generates convenience URL which points to the loopback address (localhost) on iOS, which is used to serve the simulator from the host machine. This won't work on actual hardware. You would need to replace this with an actual URL. LCMicroService.devServer() assumes the entry file is named liquid.js and the server is running on port 8082. Both of these assumptions can be changed by providing arguments, e.g. LCMicroService.devServer(fileName:"another_file.bundle", port:8888) would generate a URL to fetch a bundle with an entry point of another_file.js on port 8888.

Building the LiquidCore iOS framework

If you are interested in building the library directly and possibly contributing, you must do the following:

% git clone https://github.com/liquidplayer/LiquidCore.git
% cd LiquidCore/LiquidCoreiOS
% carthage build --no-skip-current

Your framework now sits in LiquidCoreiOS/Carthage/Build/iOS/LiquidCore.framework. You can also build it inside of XCode without issue.

License

Copyright (c) 2014-2018 Eric Lange. All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.

  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

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