How to return a nested array on solidity

Question

I am trying to return nested array on solidity error massage says

"browser/HISTORYMultipleStateMach.sol:22:16: TypeError: Index expression cannot be omitted. return myArray[]; ^-------^" "browser/HISTORYMultipleStateMach.sol:22:16: TypeError: Index expression cannot be omitted. return myArray[]; ^-------^" Can someone tell me what is wrong? Thank you enum State{ A, B, C }

    State[] curState;
    State[][] myArray;

    uint i=0;
    constructor(uint Machines)public{
        for(i=0;i<Machines;i++){
            curState.push(State.A);
            myArray.push(curState);
        }enter code here
    }


    function historyOfStateMachine() public{
        return myArray[];
    }


   function historyOfStateMachine() public{
        return myArray[];
    }

I removed now its saying "browser/HISTORYMultipleStateMach.sol:22:9: TypeError: Different number of arguments in return statement than in returns declaration. return myArray; ^------------^" @PiotrKamoda — Selena
– Selena, Commented Jul 30, 2019 at 9:43
how about save Machines in the outer scope (around where you declare myArray) and then do return myArray[Machines]? — Piotr Kamoda
– Piotr Kamoda, Commented Jul 30, 2019 at 10:37
Welcome to StackOverflow Selen! Can you please format your question? — Ferit
– Ferit, Commented Jul 30, 2019 at 14:32

Francis Eytan Dortort · Accepted Answer · 2019-07-31 02:51:54Z

2

To return the full array, you should remove [] in return myArray[];

Furthermore, it is not yet possible to return two levels of dynamic arrays.

As of version 0.4.19 of solidity, you could activate experimental support for arbitrarily nested arrays using the directive pragma experimental ABIEncoderV2;. In which case your code would be as follows:

pragma solidity ^0.4.19;
pragma experimental ABIEncoderV2;

contract MyContract {
    enum State{ A, B, C }

    State[] curState;
    State[][] myArray;

    uint i=0;

    constructor(uint Machines)public{
        for(i=0;i<Machines;i++){
            curState.push(State.A);
            myArray.push(curState);
        }
    }

    function historyOfStateMachine() public view returns (State[][]) {
        return myArray;
    }

}

answered Jul 31, 2019 at 2:51

Francis Eytan Dortort

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