Solidity Fast Track 2: Continue Learning Solidity Fast
Continuing to learn Solidity fast with the advanced basics
Previously we learned all of the basics in 20 minutes . If you are a complete beginner, start there and then come back here. Now we'll explore some more advanced concepts, but again as fast as possible. 1. Saving money with events We all know gas prices are out of control right now, so it's more...
What's coming in the Berlin Hardfork?
Looking at all the details of the upcoming fork
The Berlin Hardfork is scheduled for April 14th after block 12,224,00. Later to be followed by the London Hardfork in July which will inculde EIP-1559 . So let's take a look at the new changes and what you need to know as a developer. EIP-2929: Increased gas costs for state access EIP-2929 will...
Using 1inch ChiGas tokens to reduce transaction costs
What are gas tokens and example usage for Uniswap v2
Gas prices have been occasionally above 1000 Gwei in the past in peak times. Given an ETH price of over 1000 USD, this can lead to insane real transaction costs. In particular this can be a pain when using onchain DEX's like Uniswap, resulting in hundreds of dollars transaction fees for a single...
Openzeppelin Contracts v4 in Review
Taking a look at the new Openzeppelin v4 Release
The Openzeppelin v4 contracts are now available in Beta and most notably come with Solidity 0.8 support. For older compiler versions, you'll need to stick with the older contract versions. The beta tag means there still might be small breaking changes coming for the final v4 version, but you can...
EIP-3156: Creating a standard for Flash Loans
A new standard for flash loans unifying the interface + wrappers for existing ecosystems
As we've discussed last week, flash loans are a commonly used pattern for hacks. But what exactly are they and how are they implemented in the contracts? As of right now each protocol has its own way of implementing flash loans. With EIP-3156 we will get a standardized interface. The standard was...
Tornado.cash: A story of anonymity and zk-SNARKs
What is Tornado.cash, how to use it and the future
With the recent Yearn vault v1 hack from just a few days ago, we can see a new pattern of hacks emerging: Get anonymous ETH via tornado.cash . Use the ETH to pay for the hack transaction(s). Use a flash loan to decrease capital requirements. Create some imbalances given the large capital and...
High Stakes Roulette on Ethereum
Learn by Example: Building a secure High Stakes Roulette
It's always best to learn with examples. So let's build a little online casino on the blockchain. We'll also make it secure enough to allow playing in really high stakes by adding a secure randomness generator. Let's discuss the overall design first. Designing the contract Before we program...
How to implement generalized meta transactions
We'll explore a powerful design for meta transactions based on 0x
Enabling meta transactions inside your contract is a powerful addition. Requiring users to hold ETH to pay for gas has always been and still is one of the biggest user onboarding challenges. Who knows how many more people would be using Ethereum right now if it was just a simple click? But...
Utilizing Bitmaps to dramatically save on Gas
A simple pattern which can save you a lot of money
As you may know the most expensive operation in Ethereum is storing data ( SSTORE ). So you should always look for ways to reduce the storage requirements. Let's explore a particularly useful one: Bitmaps. How to implement a simple Bitmap Let's assume we want to store 10 boolean values. Usually...
Using the new Uniswap v2 as oracle in your contracts
How does the Uniswap v2 oracle function and how to integrate with it
We've covered Uniswap previously here . But let's go through the basics first again. What is UniSwap? If you're not familiar with Uniswap yet, it's a fully decentralized protocol for automated liquidity provision on Ethereum. An easier-to-understand description would be that it's a decentralized...
Smock: The powerful mocking tool for Hardhat
Features of smock and how to use them with examples
We’ve covered mocking contracts before , but now there’s an additional great tool available: smock . It simplifies the mocking process greatly and also gives you more testing power. You’ll be able to change the return values for functions as well as changing internal contract storage directly!...
How to build and use ERC-721 tokens in 2021
An intro for devs to the uniquely identifying token standard and its future
The ERC-721 standard has been around for a while now. Originally made popular by blockchain games, it's more and more used for other applications like Defi. But what exactly is it? A non-fungible token (NFT) is a uniquely identifying token. The word non-fungible implies you cannot just replace...
Trustless token management with Set Protocol
How to integrate token sets in your contracts
With Set Protocol you can create baskets of tokens that give users different levels of exposure to underlying assets (currently only ERC-20 tokens). Set Protocol and their TokenSet functionality is the perfect example for making use of the new paradigm of Defi and composability. You can let...
Exploring the new Solidity 0.8 Release
And how to upgrade your contracts to Solidity 0.8
We are getting closer to that Solidity 1.0 release (unless of course after 0.9 comes 0.10). Now Solidity 0.8 has been released only 5 months after the 0.7 release ! Let's explore how you can migrate your contracts today... New features & how to use them Let's look at the two big new features...