struct buyer {
uint amount;
Status status;
}
mapping(address=>buyer) public buyers;
mapping(uint=>address) buyerIndex;
uint public buyerNum;
// Order a product.
function() {
uint doubleValue=value*2;
uint amount=msg.value/doubleValue;
if(buyers[msg.sender]==null) { // Error in this line
buyer abuyer=buyer({amount:amount,status:Status.Created}); // Error in this line
buyerNum++;
buyerIndex[buyerNum]=msg.sender;
buyers[msg.sender]=abuyer;
}
else {
buyers[msg.sender].amount+=amount;
}
Order(msg.sender,amount*doubleValue,amount);
}
如果一个买家没有在买家映射中记录,那么买家数量就会增加; 但是我不知道如何判断一个买家是否在映射中。