In this video, I will teach you how to build a smart contract to organize events.There will be 2 types of users: event organizers customers Event organizers will be able to organize events and sell tickets. Customers will be able to not only buy tickets from the event organizers but…

In this video we will create a loan smart contract with Solidity. There will be 2 kind of parties interacting with the smart contract: investors borrowers The investor will send Ether at the beginning of the loan, and at the end the borrower will reimburse the investor of the initial…

Dates are a bit weird in Solidity. Solidity does have some keywords for working with dates, like now, or 1 day, but it does not have a native date type. Instead, dates are represented as integers, using timestamps in seconds. In our Truffle tests, we need to be able to…

In the last video of the smart contract testing series I showed you the basic usage of the Big Number library to deal with integers. But Big Number has many more trick up his sleeves :) In this video, I will show you all these tricks so that you feel…

In Solidity smart contract, you might have to deal with huge numbers, especially when doing financial transfers. Don't forget that we need to specify Ether transfers in Wei, a fundamental unit equals to 1 * 10 ^ -18 Ether, so very quickly even small financial values can lead to big…

In this article, I will walk you through the code of the Etherdelta smart contract: ERC20 token transfers, orders creation, and trades settlement. The smart contract is written in Solidity, and the repo is publicly accessible on the Github of Etherdelta. Decentralized exchanges are one of the most fascinating Blockchain…

Etherdelta smart contract walkthrough - Full explanation of the Solidity smart contract of Etherdelta (decentralized exchange). How the trade process work? off-chain orderbook and integration with on-chain settlement. Introducing c0x: chrome-0x extension - a chrome extension to buy ERC20 tokens, using 0x Instant and radar-relay as a backend Ethereum Support…

In Truffle tests, we have a mysterious contract() function: contract('my test', () => { if('it should ...', () => { }); }); It's Truffle replacement of Mocha describe() function, but with a twist: it defines a "clean room" and it's used to isolate tests. Very few Truffle users, but this…

In Truffle, when you write tests, you can use 'artifacts' and 'web3' objects, without defining these names: const MyContract = artifacts.require('MyContract'); //artifacts was never defined before ! const web3 = new Web3('http://localhost:8545'); //same thing for Web3! How is it possible? this is not valid Javascript! Well, this is what Truffle…

In this video, we will go through the whole process of test-driven-development (TDD) for Solidity smart contracts: writing the tests in Truffle running the failing tests with truffle test fixing the test by implementing the missing parts of the Solidity smart contract running the tests again, this time it will…