On line 22 my code is -- require(tokenContract.balanceOf(this) >= _numberOfTokens);
This gives the error message
TypeError: Member "balanceOf" not found or not visible after argument-dependent lookup in string storage ref.require(tokenContract.balanceOf(this) >= numberOfTokens); ^---------------------^
My entire code is:
pragma solidity ^0.5.1;
contract ChampTokenSale {
address admin;
string public tokenContract;
uint256 public tokenPrice;
uint256 public tokensSold;
event Sell(address _buyer, uint256 _amount);
constructor (ChampTokenSale _tokenContract, uint256 _tokenPrice) public {
admin = msg.sender;
address expected = address(this);
tokenPrice = _tokenPrice;
}
function multiply(uint x, uint y) internal pure returns (uint z) {
require(y == 0 || (z = x * y) / y == x);
}
function buyTokens(uint256 _numberOfTokens) public payable {
require(msg.value == multiply(_numberOfTokens, tokenPrice));
require(tokenContract.balanceOf(this)>= _numberOfTokens);
require(tokenContract.transfer(msg.sender, _numberOfTokens));
tokensSold += _numberOfTokens;
emit Sell(msg.sender, _numberOfTokens);
}
function endSale() public {
require(msg.sender == admin);
require(tokenContract.transfer(admin, tokenContract.balanceOf(address(this))));
admin.transfer(address(this).balance);
}
}