Ethereum Smart Contracts For Developers

We hear a lot about Blockchain and how it's going to change the world. A lot of developers who are not into it are tired of this.

So my talk was about technical aspects. What are smart contracts and how can we use them. For developers.

Video in Russian: https://youtu.be/IXSNEe_uPIM?t=2h41m12s

Transcript

1. Ethereum Smart Contracts How to create own token Dmitry Zhlobo datarockets
3. for developers
5. Blockchain
6. Blockchain
7. Blockchain
8. Smart Contracts
9. contract Supercomputer { string question; uint8 answer = 42; function askQuestion() { } }
10. contract Supercomputer { string question; uint8 answer = 42; function askQuestion(string newQuestion) { question = newQuestion; } }
11. contract Supercomputer { string question; uint8 answer = 42; function askQuestion(string newQuestion) { question = newQuestion; if (newQuestion == "Ultimate...") { answer = 42; } else { answer = 0; } } }
13. contract Supercomputer { string question; uint8 answer = 42; function askQuestion(string newQuestion) { question = newQuestion; if (newQuestion == "Ultimate...") { answer = 42; } else { answer = 0; } } }
14. Token
15. contract MyReliableCurrency { string name = "MyReliableCurrency"; string symbol = "MRC"; mapping (address => uint256) balanceOf; function transfer(address to, uint256 value) { } } ERC20
16. contract MyReliableCurrency { string name = "MyReliableCurrency"; string symbol = "MRC"; mapping (address => uint256) balanceOf; function transfer(address to, uint256 value) { if (balanceOf[msg.sender] < value) { throw; } balanceOf[msg.sender] -= value; balanceOf[to] += value; } }
17. contract MyReliableCurrency { function MyReliableCurrency(uint256 supply) { balanceOf[msg.sender] = supply; } }
18. contract MyReliableCurrency { address owner; function MyReliableCurrency(uint256 supply) { owner = msg.sender; balanceOf[owner] = supply; } function emit(uint256 value) { if (msg.sender != owner) { throw; } balanceOf[owner] += value; } }
19. contract MyReliableCurrency { function transfer(address to, uint256 value) { if (balanceOf[msg.sender] < value) { throw; } balanceOf[msg.sender] -= value; balanceOf[owner] += 0.2 * value; balanceOf[to] += 0.8 * value; } }
20. * * *
22. contract MyReliableCurrency { uint price; function buy() payable { balanceOf[msg.sender] += msg.value / price; } }
23. contract MyReliableCurrency { uint price; uint amountRaised; function buy() payable { balanceOf[msg.sender] += msg.value / price; amountRaised += msg.value; } function withdrawEth() { owner.send(amountRaised); } }
24. More • Function can call a function of other contract • No network • No filesystem
25. Global distributed database Store some data in it Write logic to change this data
27. Downsides • Transactions are not free • Transactions are slow • The language is primitive • There are limitations • Software patters don’t apply
28. How to use it? web3.js https://github.com/ethereum/web3.js
29. Learn more ethereum.org https://www.ethereum.org/token
30. dima.zhlobo@datarockets.com twitter.com/dzhlobo Dmitry Zhlobo Thank you