在合约内创建合约并通过 Web3 访问

Question

我正在 Factory 合约中创建合约 (Exchange)，我想通过 Web3 访问 Factory 合约。

?

例如，我想添加流动性，为此我需要访问 Exchange 合约。但在我想通过工厂合同中的 getExchange() 函数检查 Exchange() 合同是否已经创建之前。

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.0;

import "./Exchange.sol";

contract Factory {
    mapping(address => address) public tokenToExchange;

    function createExchange(address _tokenAddress) public returns (address) {
        require(_tokenAddress != address(0), "invalid token address");
        require(
            tokenToExchange[_tokenAddress] == address(0),
            "exchange already exists"
        );

        Exchange exchange = new Exchange(_tokenAddress);
        tokenToExchange[_tokenAddress] = address(exchange);

        return address(exchange);
    }

    function getExchange(address _tokenAddress) public view returns (address) {
        return tokenToExchange[_tokenAddress];
    }
}

如果我运行函数 getExchange(tokenAddress) 总是返回 address(0) 0x0000000000000000000000000000000000000000 的地址