Public view getter functions generated for array variables throw error

Question

contract NumberList {
    uint256[] public bigNumberList;
}

An error is generated when attempting to call the associated getter function for bigNumberList while the array is empty. E.g bigNumberList(0) generates an error. Once I've added a number to the array however, I'm able to call the getter function without any issues.

From remix the error looks like this:

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call to NumberList.bigNumberList CALL [call]from: 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4to: NumberList.bigNumberList(uint256)data: 0x35b...00000 from 0x5B38Da6a701c568545dCfcB03FcB875f56beddC4 to NumberList.bigNumberList(uint256) 0xDA0bab807633f07f013f94DD0E6A4F96F8742B53 execution cost 23744 gas (Cost only applies when called by a contract) input 0x35b...00000 decoded input { "uint256 ": "0" } decoded output { "0": "uint256: 0" } logs [] call to NumberList.bigNumberList errored: VM error: revert.

revert The transaction has been reverted to the initial state. Note: The called function should be payable if you send value and the value you send should be less than your current balance. Debug the transaction to get more information.

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As you can see the decoded output above is actually correct but I'm currently not understanding why calling the function should produce an error?

Answer 1

You could define a function that returns the length of the array

function getBigNumberListLength() public view returns(uint){
    return bigNumberList.length
}

if you need to interact with the array, you can get the length of the array first and then based on the length, you can use a valid index

Answer 2

You cannot access an invalid index from an array.

If bigNumberList is empty then calling numberList.methods.bigNumberList(index) will fail for every index.