How to pass constructor parameters to a contract using Truffle?

Question

I am using testrpc and truffle for deploying contracts.I want to pass constructor parameters while deploying.

    contract User { 
          string public userName;

          function User(string _name) {
                 userName=_name;
          }

   }

I am using contractname.deployed() for deploying contract.

      var user=User.deployed()

This deployment command won't initializes the userName parameter.

How to pass _name to this contract using truffle?

Answer 1

In Truffle, constructor params go in /migrations. So, something like:

deployer.deploy(User, "foo");

User.deployed() will be a User contract that was deployed with _name="foo"

Answer 2

Let's consider the test contract in which the constructor accepts two params:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.3;

contract Test {
    address public owner;
    address public user1;
    address public user2;

    constructor (address _user1, address _user2)  {
        owner = msg.sender;
        user1 = _user1;
        user2 = _user2;
    }
}

Truffle-test will use MyContract.new([arg1, arg2, ...], [tx params]) to pass params to the constructor:

const TestContract = artifacts.require('Test');

contract('Test', function (accounts) {
    const [owner, user1, user2] = accounts;
    const txParams = { from: owner };

    beforeEach(async function () {
        this.testContract = await TestContract.new(user1, user2, txParams);
    });

    it('has an owner, user1 and user2', async function () {
        expect(await this.testContract.owner()).to.equal(owner);
        expect(await this.testContract.user1()).to.equal(user1);
        expect(await this.testContract.user2()).to.equal(user2);
    });
});

Take into account that to access to state-variable is used the getter-function.