Blockchain By Example

Buying tokens

The main functionality of our token sale contract is defined in buying and selling tokens, which will be handled by a single function, buyTokens():

function buyTokens(uint256 _numberOfTokens)   public   payable{   require(msg.value == _numberOfTokens * tokenPrice);   require(tokenContract.balanceOf(this) >= _numberOfTokens);   tokensSold += _numberOfTokens;   emit Sell(msg.sender, _numberOfTokens);   require(tokenContract.transfer(msg.sender, _numberOfTokens));}

Let's look at what's happening in the preceding code:

• The function must be marked payable for it to accept the ether required to pay for the tokens.
  • It first requires that the ether sent with the function call, msg.value, is equal to the price of the number of tokens we want to ...