Index

ICO

  1. Chapter 1
  2. Chapter 2
  3. Chapter 3
  4. Chapter 4
  5. Chapter 5
  6. Chapter 6

Chapter 1

DappToken.sol
pragma solidity >=0.4.22 <0.7.0;

contract DappToken {
    // Initialize the smart contract with number of tokens available. 
    // To do this:
    // Constructor
    // Set the total number of tokens
    // Read the total number of tokens

    uint256 public totalSupply;

    constructor () public {
        totalSupply = 1000000;
    }


}



2_deploy_contracts.js
const DappToken = artifacts.require("DappToken");

module.exports = function(deployer) {
  deployer.deploy(DappToken);
};


Set the ganache url in truffle-config.js


Then run:
truffle migrate



Start truffle console:
truffle console


In the console run:
DappToken.deployed().then(function(i) { token=i; })


Use of then:
Because of asynchronous nature of our smart contracts, developing them relies heavily on javascript promises

This wont' work: var token = DappToken.deployed()


truffle(development)> token.address
'0xB929B577ab8cb59B28d396fD8Ac559cb62001785'


truffle(development)> token.totalSupply().then(function(s) { totalSupply = s;})
undefined




truffle(development)> totalSupply
BN {
  negative: 0,
  words: [ 1000000, <1 empty item> ],
  length: 1,
  red: null
}




truffle(development)> totalSupply.toNumber()
1000000



# To exit

truffle(development)> .exit



Tests

Truffle use mocha testing framework and chai assertion library

DappToken.js
const DappToken = artifacts.require("DappToken");

contract("DappToken", function(accounts) {
  it("sets the total supply upon deployment", function() {
    return DappToken.deployed()
      .then(function(instance) {
        tokenInstance = instance;

        return tokenInstance.totalSupply();
      })
      .then(function(totalSupply) {
        assert.equal(totalSupply.toNumber(), 1000000, "sets the total supply to 1,000,000");
      });
  });
});


truffle test


images/732-1.png

Try changing the value to 9000000 in test, an see that it will fail.