sellprice and buyprice fixing in smart contract

Question

I'facing problem when trying to put my sellPrice to 0.01 and my buyPrice equals to 0.02 in my smart contract after deployment. I intend to use setPrices function to set token price. So, I put within double quotes "10000000000000000" and "20000000000000000" because if I put without them, then it throws an exception.

Buy function:

/// @notice Buy tokens from contract by sending ether
function buy() payable public {
    uint amount = msg.value / buyPrice;               // calculates the amount
    _transfer(this, msg.sender, amount);              // makes the transfers
}

On my web3 code:

$('#buy').click(function(){
Compra.buy({
  gas: 300000,
  from: web3.eth.coinbase,
  value: 20000000000000000
},function(error,res){
console.log(res);
if(!error){
    if(res.blockHash != $("#insTrans").html())
        $("#loader").hide();

    $("#insTrans").html("Block hash: " + res.blockHash)
}else{
    $("#loader").hide();
    console.log(error);
}
});
});

When buy() is successfull, I want to add to my wallet 0.000000000000000001 of my tokens and I want 1 token on my wallet. I mean 0.02 = 1 mytokens.

Someone can help me please? I am stuck here.

Answer 1

It is due to the fact you are using decimals. If you use the standardized 18 decimal format, you need to multiply the buy price by 180 (or 10**decimals) as mentioned in the comments above.

As @smarx said above, you can change the code to

msg.value / buyPrice * 10**decimals