is there function like foreach from php in solidity? - foreach

Question

this is so important, so when i made mapping
mapping(address => uint256) balances;
i cant check all address in the list like
foreach(balances as address => balance) log(address + ":" + balance + "\n");
so if i not store all address in sorted array i well not access any address in this array, so currently i use this:
mapping(address => uint8) joiners;
address[] members;
...
if (joiners[_to] >= 1) {
joiners[_to] = 1;
members.push(_to);
}
balances[_to] += _value;
so then i can do this
uint allbalances = 0;
for(uint i; i < members.length; i++) {
allbalances = balances[members[i]];
}
return allbalances;
but this is disgusting, any one find another solution, or function like foreach from php??

Answer 1

At this moment, You can not retrieve all the keys from the solidity mapping.
https://solidity.readthedocs.io/en/v0.4.24/types.html?highlight=mapping#mappings
I think that it is good to avoid loops in the contracts unless we know what we are doing. I could not get much on what you are trying to implement from your question. If your aim is to maintain the balances per address and also the total balances, I would do something similar as shown here.
contract Balance{
mapping(address => uint) public balances;
uint public totalBalance;
function credit() payable public{
balances[msg.sender] += msg.value;
totalBalance += msg.value;
}
function debit(uint amount) public{
//conditions
require(balances[msg.sender] >= amount);
//effects
msg.sender.transfer(amount);
balances[msg.sender] -= amount;
totalBalance -= amount;
}
}
That is - Update totalBalance whenever you update the individual address balance.
Updating as per the question on the comments section:
If we need to iterate all the accounts, then we need to maintain the keys separately. My point was - total Balance would be called a lot more often than distributing profit to all accounts. So to avoid loops there for total balance calculation.
contract Ledger{
address internal manager;
mapping(address => uint) public balances;
address[] public accounts;
uint public totalBalance;
constructor() public{
manager = msg.sender;
}
function credit() payable public{
if(balances[msg.sender] == 0){
accounts.push(msg.sender);
}
balances[msg.sender] += msg.value;
totalBalance += msg.value;
}
function debit(uint amount) public{
//conditions
require(balances[msg.sender] > amount);
//effects
msg.sender.transfer(amount);
balances[msg.sender] -= amount;
totalBalance -= amount;
}
function distributeProfit(uint amountToDistribute) public {
require(manager == msg.sender);
require(amountToDistribute > 0);
//if profit might vary depends of balance, then place inside the loop.
uint profit = amountToDistribute / accounts.length;
for(uint index=0; index<accounts.length; index++){
balances[accounts[index]] += profit;
}
}
}