Contract inheritance in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a contract that inherits from another contract.

Blockchain / Solidity

contract Base {
    uint public value;
}

contract Derived is [1] {
}

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

AContract

BDerived

CBase

DValue

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong contract name after is.

Forgetting to use the is keyword.

The Derived contract inherits from Base using the is keyword followed by the base contract name.

2fill in blank

medium

Complete the code to call the base contract constructor with a value.

Blockchain / Solidity

contract Base {
    uint public value;
    constructor(uint _value) {
        value = _value;
    }
}

contract Derived is Base {
    constructor() Base([1]) {}
}

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

A10

Bvalue

CBase

D_value

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a variable name instead of a value.

Not calling the base constructor at all.

The derived contract constructor calls the base constructor with a specific value, here 10.

3fill in blank

hard

Fix the error in the code by completing the inheritance syntax correctly.

Blockchain / Solidity

contract A {
    function greet() public pure returns (string memory) {
        return "Hello from A";
    }
}

contract B [1] A {
}

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Ais

Bextends

Cimplements

Dinherits

Attempts:

3 left

💡 Hint

Common Mistakes

Using extends or inherits which are not valid in Solidity.

Forgetting the keyword entirely.

In Solidity, the correct keyword to inherit from a contract is is.

4fill in blank

hard

Fill both blanks to override a function from the base contract in the derived contract.

Blockchain / Solidity

contract Base {
    function greet() public pure virtual returns (string memory) {
        return "Hello from Base";
    }
}

contract Derived is Base {
    function greet() public pure override returns (string memory) {
        return [1];
    }
}

// Use the function to get the greeting message
// string memory message = [2];

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A"Hello from Derived"

B"Hello from Base"

CDerived().greet()

DBase().greet()

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the base message instead of the new one.

Calling the base contract's function instead of the derived one.

The derived contract overrides the greet function to return a new message. The call to Derived().greet() returns the overridden message.

5fill in blank

hard

Fill all three blanks to create a contract that inherits from two contracts and calls both base constructors.

Blockchain / Solidity

contract A {
    uint public a;
    constructor(uint _a) {
        a = _a;
    }
}

contract B {
    uint public b;
    constructor(uint _b) {
        b = _b;
    }
}

contract C is [1], [2] {
    constructor() A(1) [3](2) {}
}

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AA

BB

CA()

DB()

Attempts:

3 left

💡 Hint

Common Mistakes

Not listing both base contracts in inheritance.

Not calling both base constructors properly.

Contract C inherits from A and B. The constructor calls both base constructors with values 1 and 2 respectively.