Data Location Assignment

Austaino · August 27, 2021, 9:13am

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;
}

}

stephen_toulouse · August 30, 2021, 10:58am

Hi from france here is my code, i just replace “memory” by “storage” to store and replace the new value of the user.balance what do you think? was there a better way to do it ?

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;
    }

}

stephen_toulouse · August 30, 2021, 11:07am

is the function update the balance or add the amount to the current balance ???
if so then

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;
    }

}

MaxiRindle · August 30, 2021, 11:11am

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 {
         //We have to change ´memory´ to ´storage´ in the line below
         User storage user = users[id];
         user.balance = balance;
    }

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

}

Jay_Vanaparthy · August 30, 2021, 10:13pm

added below line in the update function

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

Djuzy_J · September 1, 2021, 11:31am

Okay guys, I’m throwing in the towel, I give up, I tried everything, but I need your help.

I’ve been trying to solve this problem for at least 6 hours straight yesterday, but no luck, no matter how logical the solution was, I tried everything. Then today, I surrendered and I said, there’s no way that I couldn’t find the solution, it must be super obvious, but long story short, I think there’s something wrong with my compiler, because as you will see in the video, I just copied the code from GitHub where the solution is, and it still didn’t work. So here it is:

Memory-assignment (No) Solution

thecil · September 1, 2021, 3:57pm

Hey @Djuzy_J, hope you are well.

From your video, i think your remix is working good, the only issue that i noticed is when you try to use the updateBalance function, which require 2 arguments (id, amount), but in the video you are just sending it 1 parameter, so then when you call getBalance to an id, it does not show the new updated balance properly.

Carlos Z

Virginia · September 1, 2021, 7:18pm

pragma solidity 0.7.5;
contract MemoryAndStorage {

mapping(uint => User) users;

struct User{
    uint id;
    uint balance;
}

uint user;
uint newbalance;


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

function updateBalance(uint id, uint newbalance) public returns (uint balance) {
     uint id;
     uint balance = newbalance;
}

function getBalance(uint id) view public returns (uint newbalance) {
    return newbalance;
}

}

Virginia · September 1, 2021, 7:26pm

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;
}

}

Mr.Flo · September 2, 2021, 5:57am

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;
    }

}

Austin_Burns · September 2, 2021, 5:37pm

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

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

}

derekryansnzy · September 5, 2021, 3:28am

I am a complete newbie to Solidity lol…so please forgive me for adding a bunch of my own notes to the code to break down the logic. But I think I was able to solve it…the testing worked anyway.

pragma solidity 0.7.5;
contract MemoryAndStorage {

    mapping(uint => User) users;

    //stored in storage
    struct User{
        uint id;
        uint balance;
    }
    // an User is defined as having an id and a balance

    function addUser(uint id, uint balance) public {
        users[id] = User(id, balance);
    }
    
    // when an user is added, that person is assigned an id and a balance,
    // in this case known as users[id]
    
        function updateBalance(uint id, uint balance) public {
         User memory user = users[id];
         users[id].balance = balance;
         
         // this function updates the balance of the user
         // the user is part of the previous function "addUser" => users[id]
         // therefore the logic is to update the balance of users[id]
    }

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

}```

JonBal · September 6, 2021, 1:11pm

Ok so i changed User memory user to User storage user, and also i changed = balance . to += 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;
    }

}

locothedev · September 7, 2021, 6:37am

simple ^^

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;
        assert(users[id].balance == balance);
    }

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

}

Pong88 · September 7, 2021, 4:37pm

// SPDX-License-Identifier: GPL-3.0
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;
    }

}

Tomster · September 8, 2021, 9:41pm

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;
    }

}

Durkey_Turkey · September 10, 2021, 12:53am

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;
}

}

Sieg · September 11, 2021, 9:25pm

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;
    }

}

DMT_RAINDROP · September 12, 2021, 6:30pm

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;
    }

}```

aidnii · September 12, 2021, 8:29pm

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

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

}