Getting the length of public array variable (getter)

Question

I am trying to get the length of array from another contact. How?

contract Lottery {
    unint[] public bets;
}

contract CheckLottery {
    function CheckLottery() {
        Lottery.bets.length;
    }
}

Fifteen

Answer 1

You have to expose the length you want as a function return value in the source contract.

The calling contract will need the ABI and contract address, which is handled via the state var and constructor below.

pragma solidity ^0.4.8;

contract Lottery {

    uint[] public bets;

    function getBetCount()
        public 
        constant
        returns(uint betCount)
    {
        return bets.length;
    }
}

contract CheckLottery {

    Lottery l;

    function CheckLottery(address lottery) {
        l = Lottery(lottery);
    }

    function checkLottery() 
        public
        constant
        returns(uint count) 
    {
        return l.getBetCount();
    }
}

Hope it helps.

Bistort

Yes it seems that, that property (method) is not exposed by default. – Fifteen

Just wondering why the getBetCount() has 6 lines? I don't have VR 360 space dome code environment, I much prefer preserve screen real estate... – Forego

Do we know why we have to use a getter for arrays but for primatives like uint256 we can just call them like in this: ethereum.stackexchange.com/questions/38317/… – Ideogram

If I understand the question ... You can use the "free" getter for public array element but there is no "free" getter for the length property of the array or the entire array. Passing entire arrays around should be avoided unless you really understand the implications. – Bistort