Overview
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.
The fabric-shim provides the chaincode interface, a lower level API for implementing "Smart Contracts". It also provides the implementation to support communication with Hyperledger Fabric peers for Smart Contracts written using the fabric-contract-api together with the fabric-chaincode-node cli to launch Chaincode or Smart Contracts.
To confirm that the fabric-shim maintains API and functional compatibility with previous versions of Hyperledger Fabric.
A more detailed explanation on the concept and programming model can be found in the smart contract processing topic.
Contract Interface
Installation
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('UpdateValuesContract');
}
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 fabric-chaincode-node
Chaincode Interface
Installation
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:
License
This package is distributed under the Apache License, Version 2.0, see LICENSE.txt for more information.