I want to test the following code in Remix. But what is the procedure?

What do I put in the input field for the function labeled set?

// https://solidity-by-example.org/mapping
// Mapping
// Maps are created with the syntax mapping(keyType => valueType).
// The keyType can be any built-in value type, bytes, string, or any contract.
// valueType can be any type including another mapping or an array.
// Mappings are not iterable.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.13;

contract Mapping {
    // Mapping from address to uint
    mapping(address => uint) public myMap;

    function get(address _addr) public view returns (uint) {
        // Mapping always returns a value.
        // If the value was never set, it will return the default value.
        return myMap[_addr];

    function set(address _addr, uint _i) public {
        // Update the value at this address
        myMap[_addr] = _i;

    function remove(address _addr) public {
        // Reset the value to the default value.
        delete myMap[_addr];

contract NestedMapping {
    // Nested mapping (mapping from address to another mapping)
    mapping(address => mapping(uint => bool)) public nested;

    function get(address _addr1, uint _i) public view returns (bool) {
        // You can get values from a nested mapping
        // even when it is not initialized
        return nested[_addr1][_i];

    function set(
        address _addr1,
        uint _i,
        bool _boo
    ) public {
        nested[_addr1][_i] = _boo;

    function remove(address _addr1, uint _i) public {
        delete nested[_addr1][_i];

This code came from Solidity by Example.

When I implement it on Remix, I get the following screen.

enter image description here

At this point, to test it, I think I need to map an address to a uint256, so I enter the following in the field next to the set button:

["0xcf646ed6e21fd0756ec45a6be5e1057fc24a1b8308175ff0b9f97f565b594eb3", 7439]

The value of the address was a randomly generated hash (I suspect the random hash might be a problem?)

enter image description here

I expect to see the set function render the value 7439. But, instead, it throws the following error:

transact to Mapping.set errored: Error encoding arguments: Error: invalid address (argument="address", value=["0xcf646ed6e21fd0756ec45a6be5e1057fc24a1b8308175ff0b9f97f565b594eb3",7439], code=INVALID_ARGUMENT, version=address/5.5.0) (argument=null, value=["0xcf646ed6e21fd0756ec45a6be5e1057fc24a1b8308175ff0b9f97f565b594eb3",7439], code=INVALID_ARGUMENT, version=abi/5.5.0)

What am I doing wrong?

1 Answer 1


You have generated a random SHA-256 that is of the format of a valid address, but it doesn't exist on the Remix's browser-based (Javascript VM) chain as any account. If it does, you might be just lucky.

If you want to use valid addresses that do exist on the browser-based VM chain, copy and use the addresses in the account section.

Account section

Also, note the input field should not contain any quotes, brackets or commas. It should look like this:

0x4B20993Bc481177ec7E8f571ceCaE8A9e22C02db, 7304

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