fabric-contract-api

The fabric-contract-api provides the contract interface. a high level API for application developers to implement Smart Contracts. Within Hyperledger Fabric, Smart Contracts are also known as Chaincode. Working with this API provides a high level entry point to writing business logic. (this contract interface is experimental, and feedback is actively requested; whilst there are no plans to change this api it might be latered as a result of feedback).

The fabric-shim provides the chaincode interface, a lower level API for implementing "Smart Contracts". It also currently provides the implementation to support communication with Hyperledger Fabric peers for Smart Contracts written using the fabric-contract-api. To confirm that this is the same as the fabric-shim in previous versions of Hyperledger Fabric.

Detailed explanation on the concept and programming model can be found here: http://hyperledger-fabric.readthedocs.io/en/latest/chaincode.html.

Contract Interface

Installation

npm install --save fabric-contract-api

Usage

Implement a class that ends the contract class, a constructor is needed. The other functions will be invokable functions of your Smart Contract

// updatevalues.js
'use strict';

// SDK Library to asset with writing the logic
const { Contract } = require('fabric-contract-api');

// Business logic (well just util but still it's general purpose logic)
const util = require('util');

/**
 * Support the Updating of values within the SmartContract
 */
class UpdateValuesContract extends Contract

    constructor(){
		super('org.mynamespace.updates');
	}

	async transactionA(ctx, newValue) {
		// retrieve existing chaincode states
		let oldValue = await ctx.stub.getState(key);

		await ctx.stub.putState(key, Buffer.from(newValue));

		return Buffer.from(newValue.toString());
	}

	async transactionB(ctx) {
	  //  .....
	}

};

module.exports = UpdateValuesContract

As with standard node modules make sure that this class is exported as follows.

// index.js
'use strict';

const UpdateValues = require('./updatevalues')
module.exports.contracts = ['UpdateValues'];

Note: In order to make this contract runnable in version 1.4, also install the fabric-shim module as below, and ensure that the 'start' script in package.json refers to startChaincode

  "scripts": {
	"start": "fabric-chaincode-node start"
  }

Chaincode Interface

Installation

npm install --save fabric-shim

Usage

The chaincode interface contains two methods to be implemented:

const shim = require('fabric-shim');

const Chaincode = class {
	async Init(stub) {
		// use the instantiate input arguments to decide initial chaincode state values

		// save the initial states
		await stub.putState(key, Buffer.from(aStringValue));

		return shim.success(Buffer.from('Initialized Successfully!'));
	}

	async Invoke(stub) {
		// use the invoke input arguments to decide intended changes

		// retrieve existing chaincode states
		let oldValue = await stub.getState(key);

		// calculate new state values and saves them
		let newValue = oldValue + delta;
		await stub.putState(key, Buffer.from(newValue));

		return shim.success(Buffer.from(newValue.toString()));
	}
};

Start the chaincode process and listen for incoming endorsement requests:

shim.start(new Chaincode());

API Reference

Visit fabric-shim.github.io and click on "Classes" link in the navigation bar on the top to view the list of class APIs.

Support

Tested with node.js 8.9.0 (LTS).

License

This package is distributed under the Apache License, Version 2.0, see LICENSE.txt for more information.