DEV Community: Julien Klepatch

Full Course on Solidity (Blockchain)

Julien Klepatch — Thu, 16 Jul 2020 05:29:08 +0000

I just released a full course on Solidity for beginners.

There is 0 pre-requisite necessary to follow.

The course is based on the popular game CryptoZombies: you learn smart contract programming on Ethereum by creating an army of Zombies!

If you want to get into Blockchain, learning smart contract programming is great entry point. Solidity is the most popular language for Ethereum smart contracts, so it makes sense.

If you don't know what Ethereum is, that's the most popular Blockchain, and the first one to have introduced the concept of smart contracts.

Smart contracts are little programs that run on top of the Blockchain. The 2 big advantage smart contracts are:

they can manipulate natively money (Ether and ERC20 tokens)
they are immutable The last point is important. It means smart contracts cannot be censored: they will run the EXACT code that was deployed, forever, and nobody can ever change that.

Smart contracts are also a bit more limited compared to traditional programs:

you can't store too much on them (its expensive)
you can't run computations that are very complex (its expensive)
modifying data cost money
modifying data takes time (15s to mine a block)
you can't call external APIs

These limitations are consequences of running in a Blockchain.

But even with all these limitations, smart contracts getting increasingly popular. DeFi, or Decentralized Finance is a new industry that vows to re-invent Finance on the Blockchain, to make it more decentralized, open and composable. You can assemble different DeFi projects like Lego blocks build your own DeFi projects. No need to ask for any permission. You can see that the market cap of DeFi is exploding.

But if you to want enter this wonderful world, you need to understand Solidity first, so go follow this course.

Finding a Remote Job as a Software Developer

Julien Klepatch — Wed, 22 Jan 2020 06:27:34 +0000

Finding a local job is not too difficult... ... but finding a remote job is way harder

I have actually found several remote jobs in the past, and here are a few tips:

Specialize in a niche - a generalist will really struggle to stand out...
Prefer Frontend to Backend & Devops, as employers are reluctant to give the custody of customer data to someone who live far away
If you are too junior, it will be hard, so try to get some "easy" remote working experience by freelancing

Introduction to Ethereum ERC20 tokens for beginners

Julien Klepatch — Thu, 14 Nov 2019 04:57:10 +0000

ERC20 tokens are the most popular type of tokens on Ethereum. They can represent fungible assets like company shares, virtual currencies, vouchers, etc..

In this ERC20 token tutorial, I will walk you through the specification of ERC20. We will go through all the functions of the specification, including the transfer functions:

simple transfer with transfer()
delegated transfer with approve + transferFrom()

For delegated transfers I will give you a practical example by explaining how decentralized exchanges (DEX) transfer tokens with approve and transferFrom.

If you are a developers who want to understand how erc20 work and how you can transfer erc20 in your smart contract, this video is for you :)

How to FORK the Ethereum Blockchain in 5s?

Julien Klepatch — Mon, 11 Nov 2019 04:13:27 +0000

Did you know that you could fork any Ethereum network with Ganache CLI?

This is a secret feature that nobody knows about, but is very powerful nonetheless.

In this video I will show you how to fork mainnet + unlock real mainnet accounts with Ganache CLI, so that you can easily test your Ethereum smart contracts.

In the example I we will transfer some Dai, using an unlocked account from mainnet (i.e WITHOUT knowing its private key).

Full playlist on Ganache CLI here

Is it HARD to get into Blockchain as a web developer?

Julien Klepatch — Fri, 08 Nov 2019 04:14:56 +0000

If you are a web developer and want to learn Blockchain, is it hard or easy?

There is a lot of misconceptions on this topic.

Actually, Blockchain is based on web technologies and there are a lot of your current knowledge that you can leverage.

Watch this video to find out if it's hard to to get into Blockchain as a web developer.

What is Ethereum Gas

Julien Klepatch — Mon, 28 Oct 2019 04:39:26 +0000

When you develop decentralized applications on Ethereum, quickly you will stumble upon the concept of Gas.

This is very confusing to a lot of developers, but it's more simple that it seems.

In this video, I will give you a quick introduction to Gas, with simple questions & answers:

What is Gas?
Who pays Gas?
Who receives Gas?
When Gas is paid?
How to pay Gas?

The 2 ways to transfer ERC20 Tokens in Solidity

Julien Klepatch — Sat, 19 Oct 2019 04:38:00 +0000

With ERC20 tokens, there are 2 APIs to transfer tokens:

transfer() (simple transfers)
transferFrom() (delegated transfer)

For transfer(), there are 3 steps:

Import the ERC20 token
Import the address of the token
Call transfer()

For transfer(), there are 4 steps:

Import the ERC20 token
Import the address of the token
Call approve()
Call transferFrom()

WATCH Whole Solidity tutorial series:

Full Ethereum Dapp Tutorial - 5h Course For Beginners

Julien Klepatch — Mon, 07 Oct 2019 17:13:15 +0000

I have just released a MONSTER FREE tutorial for building Ethereum Dapps on the FreeCodeCamp channel. We build 5 Dapps together.

It covers Solidity smart contracts, Solidity testings with Truffle, and frontend integration with Web3.

This is an extract of Dapp 30, my full Ethereum course where we build 30 Dapps.

How to choose the right variable in Solidity?

Julien Klepatch — Tue, 01 Oct 2019 04:22:13 +0000

In Solidity smart contracts, there are 3 types of variable:

Fixed-size types
Variable-size types
User-defined types

There are many different kind of variables, but the one I used the most are:

uint, to represent numbers, like amount for ether / ERC20 token transfers
address to specify recipient of transfers
arrays, to represent collection of data
mappings to also represent collection of data but this time when we want easy retrieval with a key
struct to represent some structured data, like a user

The full video is available here:

QUESTION: How to make sure dev.to posts SEO will NOT be above original content?

Julien Klepatch — Thu, 29 Aug 2019 01:28:42 +0000

I have noticed that several of my submissions here have a better SEO that the original article mentioned in the post, for the same keyword. That really turns me off to post more stuff here :( Is there a way to avoid this?

How I found a job in crypto / blockchain

Julien Klepatch — Fri, 26 Jul 2019 12:30:10 +0000

How to find a job as a blockchain developer? I will tell you the REAL STORY of how I found 2 jobs of blockchain developer. I will tell you how you can use the same tricks to find your blockchain job.

100 question & answers for Solidity job interviews

Julien Klepatch — Mon, 15 Jul 2019 21:07:16 +0000