Storage layout in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a storage variable in Solidity.

Blockchain / Solidity

contract Storage {
    uint256 public [1];
}

Drag options to blanks, or click blank then click option'

AstorageValue

BmemoryVar

Ctemp

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'memoryVar' which suggests memory instead of storage.

Using temporary names like 'temp' which are unclear.

The variable storageValue is declared as a storage variable of type uint256.

2fill in blank

medium

Complete the code to read a storage variable inside a function.

Blockchain / Solidity

contract Storage {
    uint256 public storedData;
    function getData() public view returns (uint256) {
        return [1];
    }
}

Drag options to blanks, or click blank then click option'

AstoredData()

Bthis.storedData

CstoredData

DgetData

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'storedData()' which is incorrect syntax for variables.

Using 'getData' which is the function name, not the variable.

To return the value of a storage variable, just use its name storedData.

3fill in blank

hard

Fix the error in the code to correctly update a storage variable.

Blockchain / Solidity

contract Storage {
    uint256 public count;
    function increment() public {
        count [1] 1;
    }
}

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A=

B+=

C-=

D*=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' which replaces the value instead of adding.

Using '-=' which decreases the value.

The operator += adds 1 to the current value of count.

4fill in blank

hard

Fill both blanks to declare and initialize a mapping in storage.

Blockchain / Solidity

contract Storage {
    mapping(address => [1]) public balances;
    function setBalance(address user, uint256 amount) public {
        balances[user] [2] amount;
    }
}

Drag options to blanks, or click blank then click option'

Auint256

B=

C+=

Daddress

Attempts:

3 left

💡 Hint

Common Mistakes

Using '+=' which adds to the existing value instead of setting it.

Using 'address' as the value type instead of 'uint256'.

The mapping stores uint256 values for each address. To set a balance, use the assignment operator =.

5fill in blank

hard

Fill both blanks to create a struct, declare a storage variable, and update its field.

Blockchain / Solidity

contract Storage {
    struct User  { {
        uint256 id;
        string name;
    }
    User public {BLANK_2}};
    function setUser(uint256 _id, string memory _name) public {
        [2].id = _id;
        {{BLANK_3}}.name = _name;
    }
}

Drag options to blanks, or click blank then click option'

A {

Buser

DUser

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting the opening brace '{' after struct name.

Using 'User' instead of the variable name when updating fields.

The struct body starts with a brace '{'. The storage variable is named user. Inside the function, we update user's fields.