Help with Mapping

[zchuanru]

Hi All,

I am trying to understand mapping.
I got the code from a website below:
https://www.devtwins.com/blog/understanding-mapping-vs-array-in-solidity

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract test {

    mapping (address => uint) highscores;

    address playerOne = "0xf39Fd6e51aad23F6F4cd6aB9927279cggFb91166";

    highscores[playerOne] = 750;

}

When I tried to compile, I get an error. I do not understand why there is an error.

Does anyone know?

[alymurtazamemon]

@solarwhale because you are assigning a string to an address.

address playerOne = "0xf39Fd6e51aad23F6F4cd6aB9927279cggFb91166";

remove the quotes and try again.

[zchuanru]

I removed the quotes but still there is error. I think there is something wrong with the address then I changed it to msg.sender but now the error is in the last line

//SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract test {

    mapping (address => uint) highscores;

    address playerOne = msg.sender;

    highscores[playerOne] = 750;

}

 highscores[playerOne] = 750;

it gives "ParserError: Expected identifier but got '='

[alymurtazamemon]

@solarwhale because you are assigning it in the contract, should create a function or constructor for it.

[zchuanru]

Yes it works now!

But why can't we assign it outside a function?

[alymurtazamemon]

@solarwhale read this here: https://stackoverflow.com/a/71373691/10131684

[zchuanru]

Thanks for your help!