What is the correct way of launching contract from contract

Question

Simplified version of my contracts works

MyContract

await contract.methods.info().call() Works indicating that there is no error in the MyContract itself.

Launchpad

There is no issues when launching MyContract using launchpad contract since I get address to a newly published contract.

The problem is that when I call the contract created with Launchpad contract in JavaScript I get the following error

Uncaught (in promise) Error: Couldn't decode uint256 from ABI: 0x

contract MyContract {
  function info() external view returns(uint min, uint max) {
    return(1, 2);
  }
}

contract Launchpad {

 function launch() public returns(address) {
   MyContract myContractAddress = new MyContract();
   return myContractAddress;
 }

}

"since I get address to a newly published contract" <-- How? Transactions don't have return values, so when you call launch, there's no way for you to get back the address of the new contract. The typical solution is to log an event and read that from JavaScript. — user19510, May 09 '18 at 12:50
Or you can just add pure to the declaration of function launch. — goodvibration, May 09 '18 at 12:51
return myContractAddress gives me the address to the new contract — Arash Kiani, May 09 '18 at 12:52
Only inside the blockchain. If you want to get it on the off-chain side (for example, via web3.js), then you need to decode the hash that it returns. That is, of course, unless the function is either pure or view, in which case, you can indeed obtain the return value on the off-chain side without any decoding required. So as I mentioned on the previous comment, just add pure (which you can, since the function does not access any global variables). — goodvibration, May 09 '18 at 12:52
const response = await foo.send({from: address, gas: '600000'}) — Arash Kiani, May 09 '18 at 12:55
which returns => response.to (is this not the contract address? ) — Arash Kiani, May 09 '18 at 12:56
Right. So now foo holds a hash of the transaction receipt, which you need to decode. And by the way, since you do not emit an event which contains myContractAddress in the launch function, this value is not going to be available to you even after you decode the hash. — goodvibration, May 09 '18 at 12:56
Just tested it in remix and I think you are right, apparently I was logging something else Thank you — Arash Kiani, May 09 '18 at 13:13
Possible duplicate of What is the difference between a transaction and a call? — Ismael, May 10 '18 at 17:30

What is the correct way of launching contract from contract

0 Answers0