Data Location Assignment

livermore123 · August 11, 2021, 3:11am

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

This function just change a copy (local variable named user) inside the function, so the balance can’t be updated

livermore123 · August 11, 2021, 3:16am

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;
    }

}

AtomosNucleous · August 12, 2021, 2:13pm

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    struct User{
        uint id;
        uint balance;
    }

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

}

derekdewit11 · August 13, 2021, 7:55pm

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

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

}

The code also // also dit the job.

Nilanga_Saluwadana · August 15, 2021, 6:27pm

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].balance += balance;
    }

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

}

JRSmith88 · August 15, 2021, 7:56pm

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 {
         User storage user = users[id];
         user.balance = balance;
    }

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

}```

rafow · August 16, 2021, 10:29pm

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;
}

}

nexto · August 19, 2021, 5:55am

pragma solidity 0.8.1;
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;
}

}

BallzOfCheeze · August 19, 2021, 4:46pm

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];
         users[id].balance = balance;
    }

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

}

einar27 · August 20, 2021, 3:32pm

Here is my solution. Skipped required and assertions because this assignment is focusing on data locations. Think updating balance instead of adding is a bit weird but that’s the assignment description I guess

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;
    }
}

Ali_H · August 21, 2021, 10:54am

. The solution involves changing the function “memory” to “storage” because memory only allows for temporary data storage while storage allows for data to be stored permanently:

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;
}

}

david.maluenda · August 22, 2021, 10:45am

Hi, I just added "storage instead of memory in the updateBalance function and Voila!

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;
}

}

andrequintino · August 23, 2021, 9:59pm

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;
        
    }

}

Jordi_V · August 24, 2021, 5:22pm

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]; //memory changed to storage
     user.balance = balance;
}

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

}

jakerichguy · August 24, 2021, 6:52pm

This was actually quite easy. The problem was that he used memory instead of storage and if you use memory it can only be used through the function

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;
    }

}

Artrex_G · August 25, 2021, 8:16am

pragma solidity 0.8.4;
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;
}

}

Trent · August 25, 2021, 11:53am

Did you run this to see if it would work?

Trent · August 25, 2021, 11:56am

I worked with some thoughts before looking at some other’s solutions before I realized how simple the solution was. Admittedly I did try other more complicated ideas that now seem ridiculous.

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];
         users[id].balance += balance;
    }

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

}

drawwerdna · August 25, 2021, 9:50pm

Change "memory" to "storage"

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;
    }

}

Fernando_Ribas · August 27, 2021, 1:27am

Here is my solution:


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;
    }

}