Link library inside contract creation

Question

I have a contract like this

pragma solidity ^0.4.24;

import './MyLibrary.sol';

contract A {
  // Do Stuff
}

And I have a factory contract instanciating A contracts

pragma solidity ^0.4.24;

import './A.sol';

contract B {
  mapping(uint => address) instances;
  function newA(uint id) {
    instances[id] = new A();
  }
}

I want to use B as a factory, and A is calling MyLibrary regularly. Is there any way with Truffle migrations to do something like this (deploying MyLibrary on the network, and then linking each A deployed contracts with the library)? It's easy to link a library to a contract during deployment, but I don't know how to do it dynamically on the blockchain.

Answer 1

Since B is instantiating A, and A is using the library. B will need to be linked to the library just like it is the case for A.

So in your truffle migration script, you would do the following:

deployer.then(async function() {
    await deployer.deploy(MyLibrary);
    await deployer.link(MyLibrary, [A, B]);
    await deployer.deploy(b);

    var b = await B.deployed();

    await b.newA(100);
});