Here's my function:

function Test() constant returns (uint[]) {
   var myArray = uint[];
   return myArray;

Here's an error I get in the solidity online compiler:

ballot.sol:25:9: Error: Member "push" not found or not visible after argument-dependent lookup in type(uint256[] memory) myArray.push(123);

2 Answers 2


You need to use an array in storage because it is not possible to resize memory arrays.

contract D { 
    uint[] myArray;
    function Test() constant returns (uint[]) {
       return myArray;

Otherwise you need to define the size of the array during initialization:

contract C {
    function f(uint len) {
        uint[] memory a = new uint[](7);
        bytes memory b = new bytes(len);
        // Here we have a.length == 7 and b.length == len
        a[6] = 8;
  • 1
    Oh, I get it now, thank you for your time and knowledge!
    – manidos
    Commented Jan 20, 2017 at 9:02
  • 1
    It was so simple I completely missed it Commented Sep 30, 2017 at 6:36
  • 6
    If we need a memory array inside a function, but wen don't know the items count, what can we do? Thank you!
    – Suge
    Commented Dec 24, 2017 at 5:50
  • 4
    @Suge I suggest asking a separation question with more details and be careful to avoid meta.stackexchange.com/questions/66377/what-is-the-xy-problem
    – eth
    Commented Dec 30, 2017 at 13:52

You could define the array with the length of the array you want to filter. Problem is all the tail of empty elements.

uint[] memory filteredArray = new uint[](fullArray.length);
a[0] = 1;

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