0

I define a balance as follows :

mapping (address => uint[]) Energy_Balance

to keep the history of each transaction. I set its new value as follows :

First Transaction: balances[owner][0] = balances[owner][0] + value; 
Second Transaction: balances[owner][1] = balances[owner][1] + value;

Now, I want to define a uint counter such that it can keep its last value every time it is increased one unit as follows :

balances[owner][counter] = balances[owner][counter] + value

If I define counter as follows, is it correct in solidity and it can keep its last value ?

static uint counter = 0;
function myFunction(uint value) {
    balances[owner][counter] = balances[owner][counter] + value;
    counter = counter +1;
}
2

You can simplify.

function myFunction(uint value) {
  balances[owner].push(value);
}

Also, some useful getters:

function getOwnerValueCount(address owner) returns(uint count) {
  return balances[owner].length;
}

Add public to your mapping for Energy_Balances and you will get a "free" getter approximately:

function Energy_Balances(address owner, uint row) public view returns(uint) {
  return Energy_Balances[owner][row];
}

Aside: It would be more conventional to camelCase energyBalances.

Hope it helps.

  • Thankyou. do you mean in case of using "energyBalances[owner].push(value);" I don't need to define energyBalances as an array like this : mapping (address => uint[]) energyBalances ? – Questioner Apr 27 '18 at 13:10
  • No. Assuming you did. mapping (address=>uint []) means there's an array each address. push appends another row, so you don't need to manage the counter yourself. – Rob Hitchens - B9lab Apr 27 '18 at 14:08

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.