Contract address can be precomputed, before the contract is deployed, using create2
// SPDX-License-Identifier: MIT
pragma solidity ^0.7.6;
contract Factory {
event Deployed(address addr, uint256 salt);
// 1. Get bytecode of contract to be deployed
// NOTE: _owner and _foo are arguments of the TestContract's constructor
function getBytecode(address _owner, uint _foo) public pure returns (bytes memory) {
bytes memory bytecode = type(TestContract).creationCode;
return abi.encodePacked(bytecode, abi.encode(_owner, _foo));
}
// 2. Compute the address of the contract to be deployed
// NOTE: _salt is a random number used to create an address
function getAddress(bytes memory bytecode, uint _salt) public view returns (address) {
bytes32 hash = keccak256(
abi.encodePacked(
bytes1(0xff),
address(this),
_salt,
keccak256(bytecode)
)
);
// NOTE: cast last 20 bytes of hash to address
return address(uint160(uint256(hash)));
}
// 3. Deploy the contract
// NOTE:
// Check the event log Deployed which contains the address of the deployed TestContract.
// The address in the log should equal the address computed from above.
function deploy(bytes memory bytecode, uint _salt) public payable {
address addr;
/*
NOTE: How to call create2
create2(v, p, n, s)
create new contract with code at memory p to p + n
and send v wei
and return the new address
where new address = first 20 bytes of keccak256(0xff + address(this) + s + keccak256(mem[pā¦(p+n)))
s = big-endian 256-bit value
*/
assembly {
addr := create2(
callvalue(), // wei sent with current call
// Actual code starts after skipping the first 32 bytes
add(bytecode, 0x20),
mload(bytecode), // Load the size of code contained in the first 32 bytes
_salt // Salt from function arguments
)
if iszero(extcodesize(addr)) {
revert(0, 0)
}
}
emit Deployed(addr, _salt);
}
}
contract TestContract {
address public owner;
uint public foo;
constructor(address _owner, uint _foo) payable {
owner = _owner;
foo = _foo;
}
function getBalance() public view returns (uint) {
return address(this).balance;
}
}
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