How to resolve this issue?
Here is my CROWDSALE contract:
pragma solidity ^0.5.0;
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.5.1/contracts/crowdsale/Crowdsale.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.5.1/contracts/crowdsale/validation/CappedCrowdsale.sol";
import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.5.1/contracts/crowdsale/validation/TimedCrowdsale.sol";
contract ExampleTokenCrowdsale is CappedCrowdsale, TimedCrowdsale{
//minimum investor Contribution - 0.1 ether
//minimum investor Contribution - 1 ether
uint256 public investorMinCap = 100000000000000000;
uint256 public investorHardCap = 1000000000000000000;
mapping(address => uint256) public contributions;
constructor(uint256 _rate,
address _wallet,
ERC20 _token,
uint256 _cap,
uint256 _openingTime,
uint256 _closingTime)
Crowdsale(_rate, _wallet, _token)
CappedCrowdsale(_cap)
TimedCrowdsale(_openingTime, _closingTime)
public{
}
function _preValidatePurchase(
address _beneficiary,
uint256 _weiAmount
)
internal
{
super._preValidatePurchase(_beneficiary, _weiAmount);
uint256 _existingContribution = contributions[_beneficiary];
uint256 _newContribution = _existingContribution.add(_weiAmount);
require(_newContribution >= investorMinCap && _newContribution <= investorHardCap);
contributions[_beneficiary] = _newContribution;
}
}
and i see error, why?