What is Embark

Embark is a framework that allows you to easily develop and deploy DApps.

With Embark you can:

• Automatically deploy contracts and make them available in your JS code. Embark watches for changes, and if you update a contract, Embark will automatically redeploy the contracts (if needed) and the dapp.
• Use any build pipeline or tool you wish, including grunt and meteor. (for 1.x, plugins coming soon for 2.x series)
• Do Test Driven Development with Contracts using Javascript.
• Easily deploy to & use decentralized systems such as IPFS.
• Keep track of deployed contracts, deploy only when truly needed.
• Manage different chains (e.g testnet, private net, livenet)
• Quickly create advanced DApps using multiple contracts that can interact with decentralized infrastructure for storage and comunication.

Table of Contents

• Installation
• Usage Demo
• Dashboard
• Creating a new DApp
• Libraries and APIs available
• Using and Configuring Contracts
• EmbarkJS
• EmbarkJS - Storage (IPFS)
• EmbarkJS - Communication (Whisper)
• Testing Contracts
• Working with different chains
• Custom Application Structure
• Deploying to IPFS
• LiveReload Plugin
• Donations

Installation

Requirements: geth (1.4.4 or higher), node (5.0.0) and npm Optional: serpent (develop) if using contracts with Serpent, testrpc or ethersim if using the simulator or the test functionality. Further: depending on the dapp stack you choose: IPFS

$ npm -g install embark

# If you plan to use the simulator instead of a real ethereum node.
$ npm -g install ethereumjs-testrpc

See Complete Installation Instructions.

updating from embark 1

Embark's npm package has changed from embark-framework to embark, this sometimes can create conflicts. To update first uninstall embark-framework 1 to avoid any conflicts. npm uninstall -g embark-framework then npm install -g embark

Usage - Demo

You can easily create a sample working DApp with the following:

$ embark demo
$ cd embark_demo

You can run a REAL ethereum node for development purposes:

$ embark blockchain

Alternatively, to use an ethereum rpc simulator simply run:

$ embark simulator

By default embark blockchain will mine a minimum amount of ether and will only mine when new transactions come in. This is quite usefull to keep a low CPU. The option can be configured at config/blockchain.json. Note that running a real node requires at least 2GB of free ram, please take this into account if running it in a VM.

Then, in another command line:

$ embark run

This will automatically deploy the contracts, update their JS bindings and deploy your DApp to a local server at http://localhost:8000

Note that if you update your code it will automatically be re-deployed, contracts included. There is no need to restart embark, refreshing the page on the browser will do.

Dashboard

Embark 2 comes with a terminal dashboard.

The dashboard will tell you the state of your contracts, the enviroment you are using, and what embark is doing at the moment.

available services

Available Services will display the services available to your dapp in green, if one of these is down then it will be displayed in red.

logs and console

There is a console at the bottom which can be used to interact with contracts or with embark itself. type help to see a list of available commands, more commands will be added with each version of Embark.

Creating a new DApp

If you want to create a blank new app.

$ embark new AppName
$ cd AppName

DApp Structure

  app/
    |___ contracts/ #solidity or serpent contracts
    |___ html/
    |___ css/
    |___ js/
  config/
    |___ blockchain.json #environments configuration
    |___ contracts.json  #contracts configuration
  test/
    |___ #contracts tests

Solidity/Serpent files in the contracts directory will automatically be deployed with embark run. Changes in any files will automatically be reflected in app, changes to contracts will result in a redeployment and update of their JS Bindings

Libraries and languages available

Embark can build and deploy contracts coded in Solidity or Serpent. It will make them available on the client side using EmbarkJS and Web3.js.

Further documentation for these can be found below:

• Smart Contracts: Solidity and Serpent
• Client Side: Web3.js and EmbarkJS

Using Contracts

Embark will automatically take care of deployment for you and set all needed JS bindings. For example, the contract below:

# app/contracts/simple_storage.sol
contract SimpleStorage {
  uint public storedData;

  function SimpleStorage(uint initialValue) {
    storedData = initialValue;
  }

  function set(uint x) {
    storedData = x;
  }
  function get() constant returns (uint retVal) {
    return storedData;
  }
}

Will automatically be available in Javascript as:

# app/js/index.js
SimpleStorage.set(100);
SimpleStorage.get().then(function(value) { console.log(value.toNumber()) });
SimpleStorage.storedData().then(function(value) { console.log(value.toNumber()) });

You can specify for each contract and environment its gas costs and arguments:

# config/contracts.json
{
  "development": {
    "gas": "auto",
    "contracts": {
      "SimpleStorage": {
        "args": [
          100
        ]
      }
    }
  }
}

If you are using multiple contracts, you can pass a reference to another contract as $ContractName, Embark will automatically replace this with the correct address for the contract.

# config/contracts.json
{
  ...
  "development": {
    "contracts": {
      "SimpleStorage": {
        "args": [
          100,
          $MyStorage
        ]
      },
      "MyStorage": {
        "args": [
          "initial string"
        ]
      },
      "MyMainContract": {
        "args": [
          $SimpleStorage
        ]
      }
    }
  }
  ...
}

You can now deploy many instances of the same contract. e.g

# config/contracts.json
{
  "development": {
    "contracts": {
      "Currency": {
        "deploy": false,
        "args": [
          100
        ]
      },
      "Usd": {
        "instanceOf": "Currency",
        "args": [
          200
        ]
      },
      "MyCoin": {
        "instanceOf": "Currency",
        "args": [
          200
        ]
      }
    }
  }
}
  ...

Contracts addresses can be defined, If an address is defined the contract wouldn't be deployed but its defined address will be used instead.

# config/contracts.json
{
  ...
  "development": {
    "contracts": {
      "UserStorage": {
        "address": "0x123456"
      },
      "UserManagement": {
        "args": [
          "$UserStorage"
        ]
      }
    }
  }
  ...
}

EmbarkJS

EmbarkJS is a javascript library meant to abstract and facilitate the development of DApps.

promises

methods in EmbarkJS contracts will be converted to promises.

  var myContract = new EmbarkJS.Contract({abi: abiObject, address: "0x123"});
  myContract.get().then(function(value) { console.log("value is " + value.toNumber) });

deployment

Client side deployment will be automatically available in Embark for existing contracts:

  SimpleStorage.deploy().then(function(anotherSimpleStorage) {});

or it can be manually definied as

  var myContract = new EmbarkJS.Contract({abi: abiObject, code: code});
  myContract.deploy().then(function(anotherMyContractObject) {});

EmbarkJS - Storage

initialization

The current available storage is IPFS. it can be initialized as

  EmbarkJS.Storage.setProvider('ipfs',{server: 'localhost', port: '5001'})

Saving Text

  EmbarkJS.Storage.saveText("hello world").then(function(hash) {});

Retrieving Data/Text

  EmbarkJS.Storage.get(hash).then(function(content) {});

Uploading a file

  <input type="file">

  var input = $("input[type=file"]);
  EmbarkJS.Storage.uploadFile(input).then(function(hash) {});

Generate URL to file

  EmbarkJS.Storage.getUrl(hash);

EmbarkJS - Communication

initialization

The current available communication is Whisper.

listening to messages

  EmbarkJS.Messages.listenTo({topic: ["achannel", "anotherchannel"]}).then(function(message) { console.log("received: " + message); })

sending messages

you can send plain text

  EmbarkJS.Messages.sendMessage({topic: "achannel", data: 'hello world'})

or an object

  EmbarkJS.Messages.sendMessage({topic: "achannel", data: {msg: 'hello world'}})

Tests

You can run specs with embark test, it will run any test files under test/.

Embark includes a testing lib to fastly run & test your contracts in a EVM.

# test/simple_storage_spec.js

var assert = require('assert');
var Embark = require('embark');
var EmbarkSpec = Embark.initTests();
var web3 = EmbarkSpec.web3;

describe("SimpleStorage", function() {
  before(function(done) {
    var contractsConfig = {
      "SimpleStorage": {
        args: [100]
      }
    };
    EmbarkSpec.deployAll(contractsConfig, done);
  });

  it("should set constructor value", function(done) {
    SimpleStorage.storedData(function(err, result) {
      assert.equal(result.toNumber(), 100);
      done();
    });
  });

  it("set storage value", function(done) {
    SimpleStorage.set(150, function() {
      SimpleStorage.get(function(err, result) {
        assert.equal(result.toNumber(), 150);
        done();
      });
    });
  });

});

Embark uses Mocha by default, but you can use any testing framework you want.

Working with different chains

You can specify which environment to deploy to:

$ embark blockchain production

$ embark run production

The environment is a specific blockchain configuration that can be managed at config/blockchain.json

# config/blockchain.json
  ...
   "livenet": {
    "networkType": "livenet",
    "rpcHost": "localhost",
    "rpcPort": 8545,
    "rpcCorsDomain": "http://localhost:8000",
    "account": {
      "password": "config/production/password"
    }
  },
  ...

Structuring Application

Embark is quite flexible and you can configure you're own directory structure using embark.json

# embark.json
{
  "contracts": ["app/contracts/**"],
  "app": {
    "css/app.css": ["app/css/**"],
    "js/app.js": ["embark.js", "app/js/**"],
    "index.html": "app/index.html"
  },
  "buildDir": "dist/",
  "config": "config/"
}

Deploying to IPFS

To deploy a dapp to IPFS, all you need to do is run a local IPFS node and then run embark ipfs. If you want to deploy to the livenet then after configuring you account on config/blockchain.json on the production environment then you can deploy to that chain by specifying the environment embark ipfs production.

LiveReload Plugin

Embark works quite well with the LiveReload Plugin

Donations

If you like Embark please consider donating to 0x8811FdF0F988f0CD1B7E9DE252ABfA5b18c1cDb1