Design Pattern Solidity: Stages
How you can design stages in your contract
contract Pool {
enum Stages {
Initialize,
Contribute,
Collect,
}
Stages public stage = Stages.Initialize;
modifier atStage(Stages _stage) {
require(
stage == _stage,
"Wrong pooling stage. Action not allowed."
);
_;
}
function init(...) external atStage(Stages.Initialize) {
...
currentStage = Stages.Contribute;
}
function contribute(...) external atStage(Stages.Contribute) {
...
if (hasContributionThresholdReached) {
currentStage = Stages.Collect;
}
}
function collect(...) external atStage(Stages.Collect) { }
}The pooling contract has three stages:
- The administrator has to set the parameters using
init(). - Users contribute funds to the pool using
contribute(). - Once sufficient funds are collected, the pool automatically goes into the last stage which then allows users to receive their share of whatever was purchased by the contract using
collect().
The staging system keeps a clear separation and access control of functions. Further, having a public stage variable makes it clear for the user as well.
Solidity Developer
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Design Pattern Solidity: Off-chain beats on-chain
Why you should do as much as possible off-chain
As you might have realized, Ethereum transactions are anything but cheap. In particular, if you are computing complex things or storing a lot of data. That means sometimes we cannot put all logic inside Solidity. Instead, we can utilize off-chain computations to help us. A very simple example...
Design Pattern Solidity: Initialize Contract after Deployment
How to use the Initializable pattern
There are a few reasons why you might want to initialize a contract after deployment and not directly by passing constructor arguments. But first let's look at an example: contract MyCrowdsale { uint256 rate; function initialize(uint256 _rate) public { rate = _rate; } } What's the advantage over...
Consensys Blockchain Jobs Report
What the current blockchain job market looks like
Consensys published their blockchain jobs report which you can checkout in their Blockchain Developer Job Kit. The most interesting aspects are Blockchain developer jobs have been growing at a rate of 33x of the previous year according to LinkedIns jobs report Typical salary is about...
Provable — Randomness Oracle
How the Oraclize random number generator works
One particularly interesting approach by Provable is the usage of a hardware security device, namely the Ledger Nano S. It uses a trusted execution environment to generate random numbers and provides a Provable Connector Contract as interface. How to use the Provable Randomness Oracle? Use the...
Solidity Design Patterns: Multiply before Dividing
Why the correct order matters!
There has been a lot of progress since the beginning of Ethereum about best practices in Solidity. Unfortunately, I have the feeling that most of the knowledge is within the circle of experienced people and there aren’t that many online resources about it. That is why I would like to start this...
Devcon 5 Applications closing in one week
Devcon 5 Applications closing
Watch out for the Devcon 5 applications. You only have one week left to apply either as Buidler Student Scholarship Press Devcon is by far the biggest and most impressive Ethereum conference in the world. And it's full of developers! I am especially excited about the cool location this year in...
Randomness and the Blockchain
How to achieve secure randomness for Solidity smart contracts?
Update 2023 : Ethereum transitioned to Proof of Stake! If you are interested in the randomness there, you can now use the updated info over at https://soliditydeveloper.com/prevrandao. When we talk about randomness and blockchain, these are really two problems: How to generate randomness in smart...