is there any way to import solidity codes with its deployed address ? or use an already deployed smart contract in my smart contract

Question

I wanna call 3 functions of 3 different smart contracts which swap, buy and sell some ERC20/ERC721 tokens. all 3 functions are of 3 different smart contracts owned by 3 different websites.

I wanna do it with of function of solidity, not by making web3 function which interact with the three contracts.

can we do it ?

Answer 1

if you want to use functions from a deployed smart contract, you can make an interface of the deployed contract inside your contract and make an instance of it. here is the example code-

pragma solidity ^0.5.17;

interface IERC20 {
event Approval(address indexed owner, address indexed spender, uint value);
event Transfer(address indexed from, address indexed to, uint value);

function name() external view returns (string memory);
function symbol() external view returns (string memory);
function decimals() external view 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);
}

interface IWETH  {
function deposit() external payable;
function withdraw(uint) external;
}

contract demo {

address weth=0xc778417E063141139Fce010982780140Aa0cD5Ab;



function getWETH() public payable {
   //IWETH(weth).deposit{value: msg.value}();
  IWETH(weth).deposit.value(msg.value)();

}
}

here I have made an interface of WETH contract deployed on testnet. Then in contract demo, I have made an instance of smart contract by it's contract address and called the smart contract function using its instance.