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I get a error when I call to the getVal function inside testToken file. The EVM return me the following:

call to testCoin.getVal errored: VM error: revert.

revert The transaction has been reverted to the initial state.

Note: The constructor should be payable if you send value.

pragma solidity ^0.4.24;

library SafeMath {
function mul(uint256 a, uint256 b) internal constant returns (uint256) {
    uint256 c = a * b;
    assert(a == 0 || c / a == b);
    return c;
}

function div(uint256 a, uint256 b) internal constant returns (uint256) {
    assert(b > 0); // Solidity automatically throws when dividing by 0
    uint256 c = a / b;
    assert(a == b * c + a % b); // There is no case in which this doesn't hold
    return c;
}

function sub(uint256 a, uint256 b) internal constant returns (uint256) {
    assert(b <= a);
    return a - b;
}

function add(uint256 a, uint256 b) internal constant returns (uint256) {
    uint256 c = a + b;
    assert(c >= a);
    return c;
}
}

// ERC20 Token Smart Contract
contract MyToken {
    
    string public constant name = "MyToken";
    string public constant symbol = "MYT";
    uint8 public constant decimals = 0;
    uint public _totalSupply = 1000000;
    uint256 public RATE = 1;
    bool public isMinting = false;
    
    using SafeMath for uint256;
    address public owner;
    
     // Functions with this modifier can only be executed by the owner
     modifier onlyOwner() {
        if (msg.sender != owner) {
            throw;
        }
         _;
     }
 
    // Balances for each account
    mapping(address => uint256) balances;
    // Owner of account approves the transfer of an amount to another account
    mapping(address => mapping(address=>uint256)) allowed;
    
    // Constructor
    constructor() public {
        owner = msg.sender; 
        balances[owner] = _totalSupply;
    }

    //allows owner to burn tokens that are not sold in a crowdsale
    function burnTokens(uint256 _value) onlyOwner {

         require(balances[msg.sender] >= _value && _value > 0 );
         _totalSupply = _totalSupply.sub(_value);
         balances[msg.sender] = balances[msg.sender].sub(_value);
         
    }
    
    
    function createTokens(uint newTokens){
        if(isMinting == true){
            require(newTokens > 0);
            balances[msg.sender] = balances[msg.sender].add(newTokens);
            _totalSupply = _totalSupply.add(newTokens);
        }
        else{
            throw;
        }
    }
    
    function endCrowdsale() onlyOwner {
        isMinting = false;
    }
    
    function startCrowdsale() onlyOwner{
        isMinting = true;
    }

    /*function changeCrowdsaleRate(uint256 _value) onlyOwner {
        RATE = _value;
    }*/

    
    function totalSupply() constant returns(uint256){
        return _totalSupply;
    }
    
    // What is the balance of a particular account?
    function balanceOf(address _owner) constant returns(uint256){
        return balances[_owner];
    }

     // Transfer the balance from owner's account to another account   
    function transfer(address _to, uint256 _value)  returns(bool) {
        require(balances[msg.sender] >= _value && _value > 0 );
        balances[msg.sender] = balances[msg.sender].sub(_value);
        balances[_to] = balances[_to].add(_value);
        Transfer(msg.sender, _to, _value);
        return true;
    }
    
// Send _value amount of tokens from address _from to address _to
// The transferFrom method is used for a withdraw workflow, allowing contracts to send
// tokens on your behalf, for example to "deposit" to a contract address and/or to charge
// fees in sub-currencies; the command should fail unless the _from account has
// deliberately authorized the sender of the message via some mechanism; we propose
// these standardized APIs for approval:
function transferFrom(address _from, address _to, uint256 _value)  returns(bool) {
    require(allowed[_from][msg.sender] >= _value && balances[_from] >= _value && _value > 0);
    balances[_from] = balances[_from].sub(_value);
    balances[_to] = balances[_to].add(_value);
    allowed[_from][msg.sender] = allowed[_from][msg.sender].sub(_value);
    Transfer(_from, _to, _value);
    return true;
}

// Allow _spender to withdraw from your account, multiple times, up to the _value amount.
// If this function is called again it overwrites the current allowance with _value.
function approve(address _spender, uint256 _value) returns(bool){
    allowed[msg.sender][_spender] = _value; 
    Approval(msg.sender, _spender, _value);
    return true;
}

// Returns the amount which _spender is still allowed to withdraw from _owner
function allowance(address _owner, address _spender) constant returns(uint256){
    return allowed[_owner][_spender];
}

event Transfer(address indexed _from, address indexed _to, uint256 _value);
event Approval(address indexed _owner, address indexed _spender, uint256 _value);
 }




pragma solidity ^0.4.24;

import './MyToken.sol';

contract testCoin {

    MyToken token;

    function getVal() constant public returns (uint256) {
    return token._totalSupply();
    }
}

I delete the calls to the payable function. But steel appearing

EDIT:

I make a simple example but the problem persist.

pragma solidity ^0.4.24;

contract Value {
    
    uint public testValue = 321;
    
}

pragma solidity ^0.4.24;

import './value.sol';


contract testCoin {

Value value;

function getVal() view public returns (uint){
    return value.testValue();
}
}
2

In the latter example “value” is an empty pointer. You do not initialize it.

Assign to it the proper value and all works flawlessly.

The easiest way is to have a constructor passing the address of the other contract:

constructor (address _DeployedContract) public {
value = Value(_DeployedContract);
}
| improve this answer | |
  • That´s it. Im was not looking at the importance of the contract address. I think that with just the import parameter was done. Thx ;D – UnexpectedCharacter Jan 18 '19 at 10:52
  • You are welcome – Rick Park Jan 18 '19 at 12:42

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