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I am trying to pass configuration values from one contract to another, so I can change them and avoid transaction fees.

I have two contracts:

pragma solidity ^0.4.23;

import "./two.sol";

contract One{

    string name;

    constructor() public{

    }

    Two two;

    function getNameFromOtherContract() public returns(string) {
        name = two.getName();
        return name;
    }
}

And second:

pragma solidity ^0.4.23;

contract Two{

    constructor() public{
    }

    function getName() external pure returns (string name) {
        name = "Amel";
    }
}

When I triger getNameFromOtherContract I get:

transact to One.getNameFromOtherContract errored: VM error: revert. revert The transaction has been reverted to the initial state.

What would be the correct syntax and solution for this approach?

1
  • Is unclear how you are planning to avoid transaction fees using this approach. Two is not deployed, or is it?
    – Jaime
    Commented May 16, 2018 at 17:03

1 Answer 1

2

1) You're one contract is not setting the variable two to the deployed two contract's address. This is why you're getting a revert error.

Rev A) fixed code

pragma solidity ^0.4.23;

import "./Two.sol";

contract One{

    string name;
    Two two;

    constructor() public{
        two = new Two();
    }

    function getNameFromOtherContract() public returns(string) {
        name = two.getName();
        return name;
    }
}

Rev B (actually setting the address of contract two via the constructor of contract one. Note: this requires two to be deployed before one)

pragma solidity ^0.4.23;

import "./Two.sol";

contract One{

    string name;
    Two two;

    constructor(address _two) public{
        require(_two != address(0));
        two = Two(_two);
    }

    function getNameFromOtherContract() public returns(string) {
        name = two.getName();
        return name;
    }
}

2) I'm not sure how you're going to accomplish this part: change them and avoid transaction fees. Please explain further and I'll be happy to assist.

3
  • I will use call functions which do not change state so there is no transaction happening which means there is no mining.
    – sensei
    Commented May 16, 2018 at 19:49
  • call functions which do not change state This means you can read variables but not change them. Changing variables require a state change - which requires a tx. Commented May 16, 2018 at 20:33
  • Correct, that’s what i want to achieve
    – sensei
    Commented May 17, 2018 at 4:34

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