How can i send back the ether which i used to buy a token in ERC20?

Question

Iam trying to write method in solidity where it checks if the given ether is enough to buy my coin. If its enough I will give them the respective amount of coins but if the ether is not enough I need to send back the ether which is getting used to buy a coin. Is there any method to do that ?

This is the method i have written to buy a coin.

function buyTokens(uint256 noOfCoins) public payable returns (bool success){
    if(CoinValue*noOfCoins <= msg.value)
    {
        balances[msg.sender] += noOfCoins;
        return true;
    }
    else{

        emit TokenIssues("You doesnt have enough balances to purchase these quartz base coins");
        msg.sender.transfer(msg.value);
        return false;
    }
}

apart from your actual problem i find 2 issues with your method. **1.** you can't return any value from a function that changes the state of your contract. **2.** If a user accidentally sends excess `ether` to buy your token, you are keeping it and not refunding the excess `ether` — Iftifar Taz, Feb 23 '19 at 07:43

score 0 · Answer 1 · answered Feb 22 '19 at 14:05

0

If the msg.value is lower then the amount you are expecting just throw in the else clause. That way the ether will be returned to the user.

answered Feb 22 '19 at 14:05

dHour

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5

`throw` is **deprecated** in `Solidity 0.5.x` – Iftifar Taz Feb 22 '19 at 17:08
Then he simple use **require** to check his condition. – dHour Feb 25 '19 at 08:09

How can i send back the ether which i used to buy a token in ERC20?

1 Answers1