Blockchain By Example

Withdrawing bids

After the auction ends, you'll need to enable bidders to get their ether back. For security reasons, it's better to adopt a withdrawal pattern —this helps us to avoid security issues that could cause funds to be lost:

function withdraw() public returns (bool){    require(now > auction_end , "can't withdraw, Auction is still open");    uint amount = bids[msg.sender];    bids[msg.sender] = 0;    msg.sender.transfer(amount);    WithdrawalEvent(msg.sender, amount);    return true;}

There is nothing new here except, as you might have noticed, the use of a new function, transfer(). Along with another function, send(), both methods enable the contract to send funds to a designated address (msg.sender). In this case, the contract sends the corresponding ...