Data Location Assignment

shiv1 · October 30, 2022, 5:54am

Minus my notes, i changed the memory keyword into the storage keyword and it worked.
My code:

pragma solidity 0.7.5;

contract MemoryAndStorage {

    //Storage = Permanently stored on the blockchain.
    //Memory =  Temporarily stored on the blockchain.
    //Must keep storage and memory seperate.
    //Calldata = Like memory but READ-ONLY. More explination next course 201.

    //Note that you don't have to declare said storage & memory keywords because Solidity automatically does it for you,
    //but if have a complex data type like array or structs, you will need to specify where to store them.


    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }
    

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
         User storage user = users[id];
         user.balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }

}

agcleland · November 9, 2022, 7:10pm

Here is my solution to the Data Location Assignment. The issue was that the function updateBalance had an error:

User memory user = user[id] should be User storage user = user[id]

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
         User storage user = users[id];
         user.balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }

}

AztecWarlord · November 13, 2022, 10:15pm

I just switched memory with storage and it worked

pragma solidity 0.8.7;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
         User storage user = users[id];
         user.balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }

}`

jenlesamuel · November 14, 2022, 1:56pm

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
        users[id].balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }

}

bruno_rocha · November 25, 2022, 11:41am

I did the both way and works. With Storate data location and Mapping manipulation.

Storage

    function updateBalance(uint id, uint balance) public {
         User storage user = users[id];
         user.balance = balance;
    }

Mapping manipulation

    function updateBalance(uint id, uint balance) public {
         users[id].balance = balance;
    }

Dimitar_Boychev · November 29, 2022, 3:29am

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
         balance[id].balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }

}

jieunpro · November 29, 2022, 9:01pm

pragma solidity 0.7.5;
contract MemoryAndStorage {

mapping(uint => User) users;

struct User{
    uint id;
    uint balance;
}

function addUser(uint id, uint balance) public {
    users[id] = User(id, balance);
}

function updateBalance(uint id, uint balance) public {
    users[id].balance = balance;
}

function getBalance(uint id) view public returns (uint) {
    return users[id].balance;
}

}

RedPa · December 7, 2022, 11:54am

here we go

pragma solidity 0.8.7;

contract MemoryAndStorage {

mapping(uint => User) users;

struct User{

    uint id;

    uint balance;

}

function addUser(uint id, uint balance) public {

    users[id] = User(id, balance);

}

function updateBalance(uint id, uint _balance) public {

     users[id] = User(id, _balance);

    // or users[id].balance = _balance

}

function getBalance(uint id) view public returns (uint) {

    return users[id].balance;

}

}

southarmz · December 28, 2022, 12:04pm

pragma solidity 0.7.5;

contract MemoryAndStorage {

mapping(uint => User) users;

struct User{

    uint id;

    uint balance;

}

function addUser(uint id, uint balance) public {

    users[id] = User(id, balance);

}

function updateBalance(uint id, uint balance) public {

     users[id].balance = balance;

}

function getBalance(uint id) view public returns (uint) {

    return users[id].balance;

}

}

Khudeja · January 5, 2023, 8:38am

pragma solidity 0.7.5;

contract DataAssignment{

mapping (uint=>User) users;

struct User {
    uint id;
    uint balance;
}

function addUser(uint _id, uint _balance) public {
    users[_id]= User(_id, _balance);
}

function updateBalance(uint _id, uint _balance) public {
    users[_id].balance = _balance;
}

function getBalance(uint _id) view public returns(uint){
    return users[_id].balance;
}

}Preformatted text

Ludwig.eth · January 5, 2023, 9:52pm

I simply changed the data location from memory to storage inside the updateBalance() function. The reason the function didnt work beforehand was that due to the memory assignment, the changes werent saved thus not affecting the state of the user balance.

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
        User storage user = users[id];
         user.balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }

}

Arkadii_Vedernikov · January 10, 2023, 2:58pm

pragma solidity 0.7.5;
contract MemoryAndStorage {

mapping(uint => User) users;

struct User{
    uint id;
    uint balance;
}

function addUser(uint id, uint balance) public {
    users[id] = User(id, balance);
}

function updateBalance(uint id, uint balance) public {
     User memory user = users[id];
     user.balance = balance;
     users[id] = user;
}

function getBalance(uint id) view public returns (uint) {
    return users[id].balance;
}

}

2mx · January 11, 2023, 5:18pm

pragma solidity 0.7.5;

contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{

        uint id;

        uint balance;

    }

    function addUser(uint id, uint balance) public {

        users[id] = User(id, balance);

    }

    function updateBalance(uint id, uint balance) public {

         users[id].balance = balance;

    }

    function getBalance(uint id) view public returns (uint) {

        return users[id].balance;

    }

}

gecko · January 11, 2023, 11:51pm

My Solution

function updateBalance(uint id, uint balance) public {
     users[id].balance = balance;
}

This was the only change that was needed to persist the new balance in the users mapping.

Madlearner · January 14, 2023, 7:02pm

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) private {
        //require(userSignature => true)
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) internal {
         User storage user = users[id];
         user.balance = balance;
    }

    function getBalance(uint id) view internal returns (uint) {
        return users[id].balance;
    }
     
}

JohnVersus · January 13, 2023, 4:33pm

This line seems unrelated or not required. Is that supposed to be a commented line🤔

modestbateman · January 14, 2023, 6:23pm

pragma solidity 0.7.5;

contract MemoryAndStorage {

mapping(uint => User) users;

struct User{

    uint id;

    uint balance;

}



function addUser(uint id, uint balance) public {

    users[id] = User(id, balance);

}

function updateBalance(uint id, uint balance) public {

     User storage user = users[id];

     user.balance = balance;

}

function getBalance(uint id) view public returns (uint) {

    return users[id].balance;

}

}
Preformatted text

Madlearner · January 14, 2023, 7:04pm

yes, i was trying something else to explore, i put the // thanks

kordjan · January 17, 2023, 7:05pm

Simply change memory to storage.

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users; //Mapping of users

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
         User storage user = users[id];
         user.balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }
}

Clarice_Hatischvili · January 26, 2023, 7:21am

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }

    function updateBalance(uint id, uint balance) public {
         User memory user = users[id];
         user.balance = balance;
    }

    function getBalance(uint id) view public returns (uint) {
        return users[id].balance;
    }

}