problem with inserting in an array code

[jeevansiddu]

I try to calculate percentage for my
this code below works

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

contract maths{
    uint k=10000;
    uint256 total=0;
    uint256 fund=10;
    uint256 public percentage;
    mapping(uint256=>uint256) public amountfunded;
    function calculateby4() public view returns(uint256){
        return ((k*2500)/10000);
    }
    function fillamountfunded() public {
        for(uint i=0;i<10;i++){
            amountfunded[i]=fund;
            // fund+=fund;
            total+=fund;
        }
        // uint256 m=999;
        // for(uint i=10;i<15;i++){
        //     amountfunded[i]=m;
        //     total+=m;
        //     // m+=m;
        // }
    }
    function calculatepercentage() public returns(uint256){
        // for(uint i=0;i<15;i++){
        //     // percentage[i]=(amountfunded[i]*1000)/total;
        // }
        uint256 z=0;
        percentage=(10*1000)/100;
        return (10*1000)/100;
    }
}

correctly in percentage the value 100 is stored , but when i convert that percentage array var into an object it throws an error

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.7.0 <0.9.0;

contract maths{
    uint k=10000;
    uint256 total=0;
    uint256 fund=10;
    uint256 public percentage;
    mapping(uint256=>uint256) public amountfunded;
    function calculateby4() public view returns(uint256){
        return ((k*2500)/10000);
    }
    function fillamountfunded() public {
        for(uint i=0;i<10;i++){
            amountfunded[i]=fund;
            // fund+=fund;
            total+=fund;
        }
        // uint256 m=999;
        // for(uint i=10;i<15;i++){
        //     amountfunded[i]=m;
        //     total+=m;
        //     // m+=m;
        // }
    }
    function calculatepercentage() public returns(uint256){
        // for(uint i=0;i<15;i++){
        //     // percentage[i]=(amountfunded[i]*1000)/total;
        // }
        uint256 z=0;
        percentage=(10*1000)/100;
        return (10*1000)/100;
    }
}

it throws ann error like

transact to maths.calculatepercentage pending ... 
transact to maths.calculatepercentage 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.
[vm]from: 0x5B3...eddC4to: maths.calculatepercentage() 0x049...A1Fd3value: 0 weidata: 0x5f4...69e10logs: 0hash: 0xdd6...e1b90

can someone tell why it is happening

[pacelliv]

Hello @jeevansiddu, first you need to declare percentage as an array, to turn it into an array you can declare it in this way:

uint256[] public percentage;

This syntax will create an empty array of uint256, then you need to fill the array with elements and only then you can access the elements and update their values.

The way you have it you are trying to access and update a value that does not exist yet.

You can append values to percentage using the push array method:

function calculatepercentage() public {
    // the array is empty, this doesn't work
    // for(uint i=0;i<15;i++){
    //     percentage[i]=(amountfunded[i]*1000)/total;
    // }

    // append the values
    for(uint256 i=0; i < 15; i++) {
        percentage.push((amountfunded[i] * 1000) / total);
    }

    // uint256 z=0;
    // percentage=(10*1000)/100;
    // return (10*1000)/100;
}

[jeevansiddu]

ohh thank you so much it worked , I totally forgot about the push method 🫡