Smart contract and Solidity
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Solidity is a programming language for writing smart contracts to be executed on the Ethereum blockchain. It is used to write smart contracts on Ethereum. A smart contract written in Solidity first gets compiled to bytecode that runs on the Ethereum Virtual Machine. Solidity contracts can store and transfer value and assets on the blockchain. They allow transactions to be enforced and changed through code rather than through legal documentation.
![Loop Gas
• Operation Gas Cost
• Transaction fee = Gas_used * Gas_price[Gwei]
1 Gwei = 0.000000001 ETH
• Gas
= Gas](https://image.slidesharecdn.com/smartcontractandsolidity-170919052746/85/Smart-contract-and-Solidity-10-320.jpg)
![pragma solidity ^0.4.0;
contract Coin{
address public minter;
mapping (address => uint ) public balances;
event Sent (address from, address to, uint amount);
function Coin() {
minter = msg.sender;
}
function mint(address receiver, uint amount) {
if (msg.sender != minter) return;
balances[receiver] += amount;
}
function send(address receiver, uint amount) {
if (balances[msg.sender] < amount) return;
balances[msg.sender] -= amount;
balances[receiver] += amount;
Sent(msg.sender, receiver, amount);
}
}
http://solidity.readthedocs.io/en/develop/introduction-to-smart-contracts.html
address
public
mapping
event
msg](https://image.slidesharecdn.com/smartcontractandsolidity-170919052746/85/Smart-contract-and-Solidity-21-320.jpg)
![pragma solidity^0.4.0;
contract Bank {
uint totalDeposit;
mapping(address=> uint) balanceOf;
function deposit() payable {
balanceOf[msg.sender] += msg.value;
totalDeposit += msg.value;
}
function withdraw(uint _amount) payable {
balanceOf[msg.sender] -= _amount;
totalDeposit -= _amount;
msg.sender.call.value(_amount)();
// msg.sender.transfer(_amount);
}
function getTotalBalance()
constant returns(uint) {
return totalDeposit;
}
function getBalance(address _account)
constant returns(uint) {
return balanceOf[_account];
}
}
payable](https://image.slidesharecdn.com/smartcontractandsolidity-170919052746/85/Smart-contract-and-Solidity-24-320.jpg)
Smart contract and Solidity
- 1. Smart Contract & Solidity Solidity winterj.me@gmail.com JungWinter
- 3. Smart Contract • • 1994 Nick Szabo • • Transaction
- 5. • • •
- 6. • • Contacting external services, Enforcing on-chain payments • (= )
- 8. Bitcoin Contract • Script • OPCODE • Output Input Public Key HASH CHECKSIG Private Key TRUE
- 9. Ethereum Contract • Turing Complete • APPLY(S)=S’ (APPLY: , S: , S’: ) • Smart Contract • Loop , Contract Account, Block Transaction , Gas
- 10. Loop Gas • Operation Gas Cost • Transaction fee = Gas_used * Gas_price[Gwei] 1 Gwei = 0.000000001 ETH • Gas = Gas
- 11. Smart Contract Code • Smart Contract Smart Contract Code • EVM(Ethereum Virtual Machine) EVM • • Mutan: C Deprecated • LLL: Low level OPCODE • Serpent: Python • Solidity: Javascript
- 13. Solidity
- 14. Solidity Hello World pragma solidity ^0.4.0; contract SimpleStorage { uint storedData; function set(uint x) { storedData = x; } function get() constant returns (uint retVal) { return storedData; } } pragma constant returns uint http://solidity.readthedocs.io/en/develop/introduction-to-smart-contracts.html
- 15. Solidity Hello World pragma solidity ^0.4.0; contract SimpleStorage { uint storedData; function set(uint x) { storedData = x; } function get() constant returns (uint retVal) { return storedData; } } pragma constant returns uint ^0.4.0 Solidity 0.5.0 npm ^1.2.3 → >=1.2.3 <2.0.0 ^0.2.3 → >=0.2.3 <0.3.0 ^0.0.3 → >=0.0.3 <0.0.4
- 16. Solidity Hello World pragma solidity ^0.4.0; contract SimpleStorage { uint storedData; function set(uint x) { storedData = x; } function get() constant returns (uint retVal) { return storedData; } } pragma constant returns uint constant State constant Gas Modifier . 0.4.16 constant view pure constant view alias pure pure
- 17. Solidity Hello World pragma solidity ^0.4.0; contract SimpleStorage { uint storedData; function set(uint x) { storedData = x; } function get() constant returns (uint retVal) { return storedData; } } pragma constant returns uint return 1
- 18. Solidity Hello World pragma solidity ^0.4.0; contract SimpleStorage { uint storedData; function set(uint x) { storedData = x; } function get() constant returns (uint retVal) { return storedData; } } pragma constant returns uint uint unsigned int uint8 uint256 uint uint256
- 19. Solidity Code → Byte Code SMART CONTRACT (http://goodjoon.tistory.com/261)
- 21. pragma solidity ^0.4.0; contract Coin{ address public minter; mapping (address => uint ) public balances; event Sent (address from, address to, uint amount); function Coin() { minter = msg.sender; } function mint(address receiver, uint amount) { if (msg.sender != minter) return; balances[receiver] += amount; } function send(address receiver, uint amount) { if (balances[msg.sender] < amount) return; balances[msg.sender] -= amount; balances[receiver] += amount; Sent(msg.sender, receiver, amount); } } http://solidity.readthedocs.io/en/develop/introduction-to-smart-contracts.html address public mapping event msg
- 22. address public mapping event msg http://solidity.readthedocs.io/en/develop/introduction-to-smart-contracts.html 20byte( ) balance( ), transfer( ) Python dict . mapping(address => uint) address key uint value dict public address public minter; function minter() returns (address) { return minter; } ), msg.sender , msg.value Wei(Ether) .data, .gas, .sig . listener
- 23. (3)— (https://medium.com/@soonhyungjung/ - - -3- - - -44a9d58d687a)
- 24. pragma solidity^0.4.0; contract Bank { uint totalDeposit; mapping(address=> uint) balanceOf; function deposit() payable { balanceOf[msg.sender] += msg.value; totalDeposit += msg.value; } function withdraw(uint _amount) payable { balanceOf[msg.sender] -= _amount; totalDeposit -= _amount; msg.sender.call.value(_amount)(); // msg.sender.transfer(_amount); } function getTotalBalance() constant returns(uint) { return totalDeposit; } function getBalance(address _account) constant returns(uint) { return balanceOf[_account]; } } payable
- 25. payable & modifier pragma solidity ^0.4.11; contract Purchase { address public seller; modifier onlySeller() { // Modifier require(msg.sender == seller); _; } function abort() onlySeller { // Modifier usage // ... } } Solidity modifier payable (https://medium.com/@ggogun/solidity -modifier- -payable-d892a833920c) Python Decorator, Ruby on Rails before_filter _; modifier .
- 26. TODO • Solidity Voting • Campaign & Crowdfunding • Custom Token
- 27. • Why Many Smart Contract Use Cases Are Simply Impossible (https:// www.coindesk.com/three-smart-contract-misconceptions/) • Calculating Costs in Ethereum Contracts (https://hackernoon.com/ether-purchase- power-df40a38c5a2f) • Gas Cost from Yellow Paper (http://bit.ly/2xfBHWN) • SMART CONTRACT - (http://goodjoon.tistory.com/253) • SMART CONTRACT (http://goodjoon.tistory.com/261) • dApp (http://www.chaintalk.io/archive/lecture/86) • Solidity (https://www.gitbook.com/book/ggs134/solidityguide) • Solidity (https://solidity.readthedocs.io/en/develop/)