Как использовать ленту цен Witnet?

Как использовать ленту цен Witnet?

Чтобы прочитать значение цены контракта Price Router, вы должны сначала определить адрес WitnetPriceRouter следующим образом:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.11;

import "witnet-solidity-bridge/contracts/interfaces/IWitnetPriceRouter.sol";

contract MyContract {
    IWitnetPriceRouter immutable public router;
    
    /**
     * IMPORTANT: pass the WitnetPriceRouter address depending on 
     * the network you are using! Please find available addresses here:
     * https://docs.witnet.io/smart-contracts/price-feeds/contract-addresses
     */
    constructor(IWitnetPriceRouter _router) {
        router = _router;
    }
    
    /// Returns the BTC / USD price (6 decimals), ultimately provided by the Witnet oracle.
    function getBtcUsdPrice() public view returns (int256 _price) {
        (_price,,) = router.valueFor(bytes4(0x24beead4));
    }
    
    /// Returns the ETH / USD price (6 decimals), ultimately provided by the Witnet oracle.
    function getEthUsdPrice() public view returns (int256 _price) {
        (_price,,) = router.valueFor(bytes4(0x3d15f701));
    }
    
    /// Returns the BTC / ETH price (6 decimals), derived from the ETH/USD and 
    /// the BTC/USD pairs that were ultimately provided by the Witnet oracle.
    function getBtcEthPrice() public view returns (int256 _price) {
        return (1000000 * getBtcUsdPrice()) / getEthUsdPrice();
    }
}

Вы также можете прочитать последние цены через JavaScript для любой валютной пары, поддерживаемой web3, с примерами:

web3 = Web3(Web3.HTTPProvider('https://mainnet.boba.network'))
abi = '[{ "inputs": [{ "internalType": "bytes32", "name": "_id", "type": "bytes32" }], "name": "valueFor", "outputs": [{ "internalType": "int256", "name": "", "type": "int256" }, { "internalType": "uint256", "name": "", "type": "uint256" }, { "internalType": "uint256", "name": "", "type": "uint256" }], "stateMutability": "view", "type": "function" }]'
addr = '0x36928Aeedaaf7D85bcA39aDfB2A39ec529ce221a'
contract = web3.eth.contract(address=addr, abi=abi)
// get last value for "Price-BOBA/USDT-6"
valueFor = contract.functions.valueFor().call("0xf723bde1")
print("Price-BOBA/USDT-6:", valueFor[0])
print("> lastTimestamp:", valueFor[1])
print("> latestUpdateStatus:", valueFor[2])

пример солидности, чтобы прочитать последнюю цену

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.11;

import "witnet-solidity-bridge/contracts/interfaces/IWitnetPriceRouter.sol";
import "witnet-solidity-bridge/contracts/interfaces/IWitnetPriceFeed.sol";

contract MyContract {

    IWitnetPriceRouter immutable public witnetPriceRouter;
    IWitnetPriceFeed public celoEurPrice;
    
    /**
     * IMPORTANT: pass the WitnetPriceRouter address depending on 
     * the network you are using! Please find available addresses here:
     * https://docs.witnet.io/smart-contracts/price-feeds/contract-addresses
     */
    constructor(IWitnetPriceRouter _router)
        witnetPriceRouter = _router;
        updateCeloEurPriceFeed();
    }
    
    /// Detects if the WitnetPriceRouter is now pointing to a different IWitnetPriceFeed implementation:
    function updateCeloEurPriceFeed() public {
        IERC165 _newPriceFeed = witnetPriceRouter.getPriceFeed(bytes4(0x21a79821));
        if (address(_newPriceFeed) != address(0)) {
            celoEurPrice = IWitnetPriceFeed(address(_newPriceFeed));
        }
    }
    
    /// Returns the CELO / EUR price (6 decimals), ultimately provided by the Witnet oracle, and
    /// the timestamps at which the price was reported back from the Witnet oracle's sidechain 
    /// to Celo Alfajores.
    function getCeloEurPrice() external view returns (int256 _lastPrice, uint256 _lastTimestamp) {
        (_lastPrice, _lastTimestamp,,) = celoEurPrice.lastValue();
    }
    
    // ...
}

источник: https://docs.witnet.io/smart-contracts/witnet-data-feeds/price-feeds-registry.