We are going to create a Smart Contract .

We are going to create a Smart Contract using truffle:

This contract will hold an associative array of addresses and integers. Each address will be associated with a number of tokens that expresses if the user identified by this address is able to use a specific service (tokens > 0) or not (tokens == 0).

Step 1 : Install truffle

It is a development framework for Ethereum. There are many others, but we will use Truffle in this tutorial, to develop and deploy our smart contract.

Step 2 : Create Project

  1. Make a folder “SmartToken”.
  2. run “truffle init” cmd on that folder.
  3. you will see three folders are created inside that folder i.e contracts, migrations, test and one node js file i.e truffle.js
  4. inside contracts folder we will create contract by default three files will be there they are also a contract but here we will create that contract in the name of “ smart-token.sol “ .contract is written in solidity language.

“pragma solidity ^0.4.0;

contract SmartToken {
mapping(address => uint) tokens;

event OnValueChanged(address indexed _from, uint _value);

function depositToken(address recipient, uint value) returns (bool success) {
tokens[recipient] += value;

OnValueChanged(recipient, tokens[recipient]);
return true;
}

function withdrawToken(address recipient, uint value) returns (bool success) {
if ((tokens[recipient] — value) < 0) {
tokens[recipient] = 0;
} else {
tokens[recipient] -= value;
}

OnValueChanged(recipient, tokens[recipient]);
return true;
}

function getTokens(address recipient) constant returns (uint value) {
return tokens[recipient];
}
}“

This contract has three functions:

  • depositToken: add some tokens to a specific address
  • withdrawToken: withdraw some token from a specific address
  • getTokens: retrieve the number of tokens available for a specific address

Step 4 : Prepare for deployment:

Before deploying the Smart Contract, you have to adjust several files in your project.

Replace the content of “migrations/2_deploy_contracts.js” with the following content in order to deploy our “SmartToken” Smart Contract:

var SmartToken = artifacts.require(“./smartToken.sol”);

module.exports = function(deployer) {

deployer.deploy(SmartToken);

};

module.exports = {
networks: {
development: {
host: “localhost”,
port: 8042,
network_id: “*” // Match any network id
}
}
};

and in truffle.js file

now start mining from miner cmd prompt.

and in another tab run following commands

  1. truffle compile
  2. truffle migrate {it will deploy contracts}
  3. truffle console
  4. inside truffle console —” smartToken.address” → “JSON.stringify(SmartToken.abi)”
  5. run it on localhost:5000

Note : http://truffleframework.com/docs

through this tutorial you can go deep into truffle.