BBc-1 と Ethereum 演習 II / Practicing BBc-1 and Ethereum II

Transcript

1. 3 BBc-1 Ethereum II CSO / ks91@blockchainhub.co.jp — 3 BBc-1

   Ethereum II — 2020-05-27 – p.1/37

2. https://speakerdeck.com/ks91 — 3 BBc-1 Ethereum II — 2020-05-27 – p.2/37

3. ( ) SFC / ( ) CSO (Chief Science Officer)

   1993 ( ) 2006 ( ) SFC 19 P2P (Peer-to-Peer) ( 9 ) 2011 2018 2019 2019 2020 “STAY HOME, ENJOY LIFE” (in Zoom) → ( ) — 3 BBc-1 Ethereum II — 2020-05-27 – p.3/37

4. BBc-1 Ethereum 3 Ethereum — 3 BBc-1 Ethereum II —

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5. 1. : ERC20 2. : 3. : — 3 BBc-1

   Ethereum II — 2020-05-27 – p.5/37

6. 1. : ERC20 $ brownie bake token — 3 BBc-1

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7. Solidity JavaScript ( , ) (constructor) ( ) ( )

   Ether Ethereum — 3 BBc-1 Ethereum II — 2020-05-27 – p.7/37

8. pragma solidity ˆ0.5.0; contract Token { ( ) : (EVM

   ) : constructor (...) public { /* */ : } function balanceOf(...) { /* ( ) */ : } : } constructor C (/* */ // ) — 3 BBc-1 Ethereum II — 2020-05-27 – p.8/37

9. ERC20 ERC (Ethereum Request for Comment) 20 https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md contract ERC20

   { function totalSupply() constant returns (uint totalSupply); function balanceOf(address _owner) constant returns (uint balance); function transfer(address _to, uint _value) returns (bool success); function transferFrom(address _from, address _to, uint _value) returns (bool success); function approve(address _spender, uint _value) returns (bool success); function allowance(address _owner, address _spender) constant returns (uint remaining); event Transfer(address indexed _from, address indexed _to, uint _value); event Approval(address indexed _owner, address indexed _spender, uint _value); } name/ , symbol/ , decimals/ approve allowance ERC223 ( ), ERC721 (Non-Fungible) — 3 BBc-1 Ethereum II — 2020-05-27 – p.9/37

10. ERC20 ERC20 ( ) ⇒ ERC20 ( ERC20 ) ERC20

    ⇒ — 3 BBc-1 Ethereum II — 2020-05-27 – p.10/37

11. (fungible) ERC20 → ERC223 (draft) or ERC777 (non-fungible) ERC721 (

    ) (partially fungible) ERC1410 (draft) (ERC1400 ) — 3 BBc-1 Ethereum II — 2020-05-27 – p.11/37

12. Token ( ) string public symbol; string public name; uint256

    public decimals; uint256 public totalSupply; mapping(address => uint256) balances; . . . name, symbol decimals : 2 100 1.00 mapping balances — 3 BBc-1 Ethereum II — 2020-05-27 – p.12/37

13. Token ( ) event Transfer(address from, address to, uint256 value);

    Token function emit Transfer() ( ) — 3 BBc-1 Ethereum II — 2020-05-27 – p.13/37

14. Token ( ) constructor( string memory _symbol, string memory _name,

    uint256 _decimals, uint256 _totalSupply ) public { symbol = _symbol; name = _name; decimals = _decimals; totalSupply = _totalSupply; balances[msg.sender] = _totalSupply; } msg.sender _totalSupply — 3 BBc-1 Ethereum II — 2020-05-27 – p.14/37

15. Token balanceOf() function balanceOf(address _owner) public view returns (uint256) {

    return balances[_owner]; } — 3 BBc-1 Ethereum II — 2020-05-27 – p.15/37

16. Token transfer() function transfer(address _to, uint256 _value) public returns (bool)

    { balances[msg.sender] = balances[msg.sender].sub(_value); balances[_to] = balances[_to].add(_value); emit Transfer(msg.sender, _to, _value); return true; } OpenZeppelin https://openzeppelin.org — 3 BBc-1 Ethereum II — 2020-05-27 – p.16/37

17. 2. — 3 BBc-1 Ethereum II — 2020-05-27 – p.17/37

18. GitHub git clone $ git clone https://github.com/ks91/sample-smart-contracts.git sample-smart-contracts contracts, scripts

    tests token Token — 3 BBc-1 Ethereum II — 2020-05-27 – p.18/37

19. (m2 ) 1 1 — 3 BBc-1 Ethereum II —

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20. IndivisibleAsset string public _name_; string public _symbol_; uint256 public _quantity_;

    address public _owner_; _name_ ( ) _symbol_ _quantity_ (m2 ) _owner_ ‘_’ Solidity . . . — 3 BBc-1 Ethereum II — 2020-05-27 – p.20/37

21. IndivisibleAsset event Transfer(address indexed from, address indexed to); from to

    indexed — 3 BBc-1 Ethereum II — 2020-05-27 – p.21/37

22. IndivisibleAsset constructor (string name, string symbol, uint256 quantity) public {

    _name_ = name; _symbol_ = symbol; _quantity_ = quantity; _owner_ = msg.sender; } — 3 BBc-1 Ethereum II — 2020-05-27 – p.22/37

23. IndivisibleAsset getOwner() function getOwner() public view returns (address) { return

    (_owner_); } — 3 BBc-1 Ethereum II — 2020-05-27 – p.23/37

24. IndivisibleAsset transfer() function transfer(address to) public returns (bool) { require(_owner_

    == msg.sender); _owner_ = to; emit Transfer(msg.sender, to); return true; } require (function ) ( ) $ brownie compile — 3 BBc-1 Ethereum II — 2020-05-27 – p.24/37

25. scripts/indivisible asset.py from brownie import * def main(): accounts[0].deploy(IndivisibleAsset, "5322

    Endo, Fujisawa", "mˆ2", 300) SFC (300m2 ) ( ) — 3 BBc-1 Ethereum II — 2020-05-27 – p.25/37

26. from brownie import * import pytest def test_owner_and_transfer(IndivisibleAsset): asset =

    accounts[0].deploy(IndivisibleAsset, "5322 Endo", "mˆ2", 300) assert asset.getOwner() == accounts[0] asset.transfer(accounts[1], {’from’: accounts[0]}) assert asset.getOwner() == accounts[1] try: asset.transfer(accounts[0], {’from’: accounts[0]}) done = 1 except: done = 0 assert done == 0 accounts[0] accounts[1] — 3 BBc-1 Ethereum II — 2020-05-27 – p.26/37

27. $ pytest tests/test_indivisible_asset.py — 3 BBc-1 Ethereum II — 2020-05-27

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28. 3. — 3 BBc-1 Ethereum II — 2020-05-27 – p.28/37

29. transfer settle, retrieve asset, retrieve token 3 — 3 BBc-1

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30. 1. ( ) 2. ( ) 3. ( ) —

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31. OneTimeEscrow settle() function settle() public returns (bool) { require(_token_.balanceOf(address(this)) >=

    _price_); /* this */ require(_asset_.getOwner() == address(this)); _token_.transfer(_seller_ , _price_); _asset_.transfer(_buyer_); emit Settled(); /* */ return true; } settle() transfer ( / ) $ brownie compile — 3 BBc-1 Ethereum II — 2020-05-27 – p.31/37

32. (1) from brownie import * import pytest def test_deploy_and_settle(Token, IndivisibleAsset,

    OneTimeEscrow): asset = accounts[0].deploy(IndivisibleAsset, "5322 Endo", "mˆ2", 300) token = accounts[0].deploy(Token, "Test Token", "TEST", 18, "1000 ether") — 3 BBc-1 Ethereum II — 2020-05-27 – p.32/37

33. (2) token.transfer(accounts[1], 300, {’from’: accounts[0]}) escrow = accounts[0].deploy(OneTimeEscrow, token, accounts[1],

    asset, accounts[0], 300) accounts[0] accounts[1] 300 300 TX accounts[1] accounts[0] 300 bake Token 300 ETH wei — 3 BBc-1 Ethereum II — 2020-05-27 – p.33/37

34. (3) token.transfer(escrow, 300, {’from’: accounts[1]}) asset.transfer(escrow, {’from’: accounts[0]}) assert token.balanceOf(accounts[0])

    == 999999999999999999700 assert token.balanceOf(accounts[1]) == 0 assert token.balanceOf(escrow) == 300 assert asset.getOwner() == escrow accounts[1] ( ) 300 accounts[0] ( ) — 3 BBc-1 Ethereum II — 2020-05-27 – p.34/37

35. (4) escrow.settle({’from’: accounts[0]}) assert token.balanceOf(accounts[0]) == 1000000000000000000000 assert token.balanceOf(accounts[1]) ==

    0 assert token.balanceOf(escrow) == 0 assert asset.getOwner() == accounts[1] settle() accounts[0] OK — 3 BBc-1 Ethereum II — 2020-05-27 – p.35/37

36. $ pytest tests/test_one_time_escrow.py : settle() — 3 BBc-1 Ethereum II

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37. 4 BBc-1 Ethereum III : — 3 BBc-1 Ethereum II

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