This document provides an overview of decentralized exchanges (DEXs) like Uniswap, including key metrics on total value locked in DeFi protocols and the growth of DEX volume. It explains the core components that power Uniswap, such as the factory contract that creates trading pairs, the pair contract that handles token swaps, and mechanisms for minting/burning liquidity. Finally, it demonstrates how to interact programmatically with Uniswap through its router contract to get price quotes, swap tokens, and integrate token trading functionality into smart contracts.

1. DEX & UNISWAP
Decentralized Exchanges
Uniswap under the Hood
Accessing Decentralized Exchanges
2/4/2021

2. GRAPH OF THE DAY

3. TOTAL VALUE LOCKED IN DEFI
Total Value Locked in DeFi protocols (TVL) now
stands above $25B, an incredible 2500% growth Y/Y.
Similarly, the number of DeFi users has surpassed 1.2M
Protocols like Uniswap and Compound claim 200-500K
users, with most other DeFi apps between 25-50K users.

4. DEX VOLUME

5. UNISWAP
Most popular decentralized exchange
August 30 surpassed major cryptocurrency exchange Coinbase in volume
after its users traded $426 million worth of cryptocurrencies in a single day

6. UNISWAP Uniswap under the hood

7. ERC20 TOKEN SWAP ON UNSWAP

8. UNISWAP EXCHANGE CONTRACT

9. MECHANICS OF SWAP

10. UNISWAP FACTORY CONTRACT

11. UNISWAP FACTORY CONTRACT IN
DETAIL
pragma solidity >=0.5.0;
interface IUniswapV2Factory {
event PairCreated(address indexed token0, address indexed token1, address pair, uint);
function getPair(address tokenA, address tokenB) external view returns (address pair);
function allPairs(uint) external view returns (address pair);
function allPairsLength() external view returns (uint);
function feeTo() external view returns (address);
function feeToSetter() external view returns (address);
function createPair(address tokenA, address tokenB) external returns (address pair);
}

12. UNISWAP PAIR CONTRACT

13. UNISWAP PAIR CONTRACT (1/3)
interface IUniswapV2Pair {
event Approval(address indexed owner, address indexed spender, uint value);
event Transfer(address indexed from, address indexed to, uint value);
function name() external pure returns (string memory);
function symbol() external pure returns (string memory);
function decimals() external pure returns (uint8);
function totalSupply() external view returns (uint);
function balanceOf(address owner) external view returns (uint);
function allowance(address owner, address spender) external view returns (uint);
function approve(address spender, uint value) external returns (bool);
function transfer(address to, uint value) external returns (bool);
function transferFrom(address from, address to, uint value) external returns (bool);
function DOMAIN_SEPARATOR() external view returns (bytes32);
function PERMIT_TYPEHASH() external pure returns (bytes32);
function nonces(address owner) external view returns (uint);
function permit(address owner, address spender, uint value, uint deadline, uint8 v, bytes32 r, bytes32 s) external;

14. UNISWAP PAIR CONTRACT (2/3)
function MINIMUM_LIQUIDITY() external pure returns (uint);
function factory() external view returns (address);
function token0() external view returns (address);
function token1() external view returns (address);
function getReserves() external view returns (uint112 reserve0, uint112 reserve1,
uint32 blockTimestampLast);
function price0CumulativeLast() external view returns (uint);
function price1CumulativeLast() external view returns (uint);
function kLast() external view returns (uint);
function mint(address to) external returns (uint liquidity);
function burn(address to) external returns (uint amount0, uint amount1);
function swap(uint amount0Out, uint amount1Out, address to, bytes calldata data)
external;
function skim(address to) external;
function sync() external;

15. UNISWAP PAIR CONTRACT (3/3)
event Mint(address indexed sender, uint amount0, uint amount1);
event Burn(address indexed sender, uint amount0, uint amount1, address indexed to);
event Swap(
address indexed sender,
uint amount0In,
uint amount1In,
uint amount0Out,
uint amount1Out,
address indexed to
);

16. UNISWAP ROUTER CONTRACT
interface IUniswapV2Router01 {
function factory() external pure returns (address);
function WETH() external pure returns (address);
function addLiquidity()
function addLiquidityETH()
function removeLiquidity()
function removeLiquidityETH()
function removeLiquidityWithPermit()
function removeLiquidityETHWithPermit()
function swapExactTokensForTokens()
function swapTokensForExactTokens()
function swapExactETHForTokens()
function swapTokensForExactETH()
function swapExactTokensForETH()
function swapETHForExactTokens()
function quote(uint amountA, uint reserveA, uint reserveB)
function getAmountOut(uint amountIn, uint reserveIn, uint reserveOut)
function getAmountIn(uint amountOut, uint reserveIn, uint reserveOut)
function getAmountsOut(uint amountIn, address[] calldata path)
function getAmountsIn(uint amountOut, address[] calldata path)
}

17. CHECK ACTIVITY OF THE ROUTER
CONTRACT

18. CHECK TRANSACTION EXECUTED
BY ROUTER

19. INTERACTING WITH
DECENTRALIZED EXCHANGE

20. ACCESSING UNISWAP DEX
WEB UI
API
SDK/Libraries
Smart Contracts

21. WEB UI (DEMO)

22. WEB UI (DEMO PART 2)

23. API ACCESS (DEMO)

24. JAVASCRIPT ACCESS DEMO

25. CALL FROM A SMART CONTRACT –
GET PRICE
IUniswapV2Router02 private uniswapV2router;
uniswapV2router =
IUniswapV2Router02(0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D);
function getEstimatedEthForToken(address token, uint256 tokenAmount) public
view returns (uint256) {
if (token!=address(0) && tokenAmount>0) {
address[] memory path = getPathToETH(token);
uint[] memory r = uniswapV2router.getAmountsOut(tokenAmount, path);
return r[1];
} else {
return 0;
}
}

26. SWAP TOKEN TO ETH
// amountOutMin must be retrieved from an oracle of some kind
address[] memory path = new address[](2);
path[0] = address(DAI);
path[1] = UniswapV2Router02.WETH();
UniswapV2Router02.swapExactTokensForETH(amountIn, amountOutMin, path,
msg.sender, block.timestamp)

27. CALL FROM A SMART CONTRACT -
SELL
event SellToken(address token, uint256 tokenAmount);
function convertTokenToEth(address token, uint256 tokenAmount) public onlyOwner {
IERC20 erc20Token = IERC20(token);
emit SellToken(token, tokenAmount);
require(getTokenBalance(token)>=tokenAmount && token!=address(0), "Token balance");
require(erc20Token.approve(address(uniswapV2router), 0), "Approve failed");
require(erc20Token.approve(address(uniswapV2router), tokenAmount), "Approve failed");
uint256 deadline = block.timestamp + 300; // transaction expires in 300 seconds (5 minutes)
uint256 minETHAmountToReceieve = (getEstimatedEthForToken(token, tokenAmount)*8)/10; //20%
sleepage is OK
uniswapV2router.swapExactTokensForETH(tokenAmount, minETHAmountToReceieve,
getPathToETH(token), address(this), deadline);
}

28. QUESTIONS?

29. OUR NEXT MEETUP

30. STAY IN TOUCH
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