Solidity – Resolving TypeError: Invalid Type for Argument in Function Call

contract-debuggingcontract-developmentsolidity

I am unable to use the 'this' Keyword in below code.

    function buyTokens(uint256 _numberOfTokens) public payable {
    require(msg.value == multiply(_numberOfTokens, tokenPrice));
    require(tokenContract.balanceOf(this) >= _numberOfTokens);(issue is here)
    require(tokenContract.transfer(msg.sender, _numberOfTokens));

giving below error.

TypeError: Invalid type for argument in function call. Invalid 
  implicit conversion from contract DappTokenSale to address requested.
    require(tokenContract.balanceOf(this) >= _numberOfTokens);

Best Answer

The comment says implicit conversion from contract DappTokenSale to address.

So just use an explicit conversion instead - change this to address(this).

Related Solutions

[Ethereum] Invalid implicit conversion from address to contract

Your error is exactly what the error message says. You are trying to implicitly convert between UpgradeableToken and address - your lower level contract passes on the parameter of type address but upper level contract expects type UpgradeableToken.

Change the contract UpgradeableToken to access an address parameter and it should be fine. You can then cast the address into a UpgradeableToken like this: UpgradeableToken tok = UpgradeableToken(_oldToken);.

P.S. What you are referring to as "primary function" is actually called a constructor. You should also use a newer version of Solidity and get used to using the constructor keyword instead of special function name - your way will no longer work starting from Solidity 0.5.

Fixing Invalid Implicit Conversion Errors from uint256 to bytes in Solidity

You are getting this error because you are trying to take the keccack256 hash of a uint, which you cannot do, according to the docs. What you must do instead is convert the uint to a bytes.

The code you want is as follows:

function random() private returns(uint){
    uint source = block.difficulty + now;
    bytes memory source_b = toBytes(source);
    return uint(keccak256(source_b));
}

function toBytes(uint256 x) public returns (bytes memory b) {
    b = new bytes(32);
    assembly { mstore(add(b, 32), x) }
}

Best Answer

Related Solutions

[Ethereum] Invalid implicit conversion from address to contract

Fixing Invalid Implicit Conversion Errors from uint256 to bytes in Solidity

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