Getting Started

Installation

Phoenix can be used in browser, node and native script environments. To get started install Phoenix using npm or yarn by executing this command in your project directory:

# Using npm
npm install --save phoenix  

# Using yarn
yarn add phoenix

Importing the library

// ESM (might require babel / browserify)
import Phoenix from 'phoenix';  

// CommonJS
const Phoenix = require('phoenix');

Connecting to a web3 provider

To interact with the EVM, Phoenix requires a valid websockets Web3 provider.

const eventSyncer = new Phoenix(web3.currentProvider);
eventSyncer.init();

In addition to the provider, Phoenix also accepts an options object with settings that can change its behavior:

dbFilename - Name of the database where the information will be stored (default 'phoenix.db')
callInterval - Interval of time in milliseconds to query a contract/address to determine changes in state or balance (default: obtain data every block).

Reacting to data

Phoenix provides tracking functions for contract state, events and balances. These functions return RxJS Observables which you can subscribe to, and obtain and transform the observed data via operators.

Tracking a contract's state

You can track changes to the contract state, by specifying the view function and arguments to call and query the contract.

const contractObject = ...; // A web3.eth.Contract object initialized with an address and ABI.
const functionName = "..."; // string containing the name of the contract's constant/view function to track.
const functionArgs = []; // array containing the arguments of the function to track. Optional
const callOptions = {from: web3.eth.defaultAccount}; //  Options used for calling. Only `from`, `gas` and `gasPrice` are accepted. Optional
eventSyncer.trackProperty(contractObject, functionName, functionArgs, callOptions)
  .subscribe(value => console.dir)

This can be used as well to track public state variables, since they implicity create a view function when they're declared public. The functionName would be the same as the variable name, and functionArgs would have a value when the type is a mapping or array (since these require an index value to query them).

Tracking contract events

You can track events and react to their returned values.

const contractObject = ...; // A web3.eth.Contract object initialized with an address and ABI.
const eventName = "..."; // string containing the name of the event to track.
const options = { filter: { }, fromBlock: 1 }; // options used to query the events. Optional

eventSyncer.trackEvent(contractObject, eventName, options)
  .subscribe(eventData => console.dir);

Tracking balances of addresses

You can also track changes in both ETH and ERC20 token balances for each mined block or time interval depending on the callInterval configured. Balances are returned as a string containing the vaue in wei.

// Tracking ETH balance
const address = "0x0001020304050607080900010203040506070809";

eventSyncer
  .trackBalance(address)
  .subscribe((balance) => {
    console.log("ETH balance is ", balance)
  });

// Tracking ERC20 balance
const address = "0x0001020304050607080900010203040506070809";
const tokenAddress = "0x744d70fdbe2ba4cf95131626614a1763df805b9e"; // SNT Address

eventSyncer.trackBalance(address, tokenAddress)
  .subscribe((balance) => {
    console.log("Token balance is ", balance)
  });

Subscriptions

You may have noticed that each tracking function has a .subscribe(). Subscriptions are triggered each time an observable emits a new value. These subscription receive a callback that must have a parameter which represents the value received from the observable; and they return a subscription.

Subscriptions can be disposed by executing the method unsubscribe() liberating the resource held by it:

const subscription = eventSyncer.trackBalance(address, tokenAddress).subscribe(value => { /* Do something */ });

// ...

subscription.unsubscribe();

Cleanup

If Phoenix eventSyncer is not needed anymore, you need to invoke clean() to dispose and perform the cleanup necessary to remove the internal subscriptions and interval timers created by Phoenix during its normal execution. Any subscription created via the tracking methods must be unsubscribed manually (in the current version).

eventSyncer.clean();

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