Abstract contracts in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an abstract contract in Solidity.

Blockchain / Solidity

abstract contract [1] {
    function doSomething() public virtual;
}

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AMyAbstract

Bcontract

Cinterface

Dlibrary

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'interface' or 'library' instead of a contract name.

Omitting the contract name.

The keyword abstract is used to declare an abstract contract. Here, MyAbstract is the contract name.

2fill in blank

medium

Complete the code to declare an abstract function inside an abstract contract.

Blockchain / Solidity

abstract contract Base {
    function [1] public virtual;
}

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AdoSomething() public

BdoSomething()

CdoSomething() public override

DdoSomething() public virtual override

Attempts:

3 left

💡 Hint

Common Mistakes

Adding a function body in an abstract function.

Using override in the abstract function declaration.

Abstract functions are declared with their signature only, ending with a semicolon. The virtual keyword allows overriding.

3fill in blank

hard

Fix the error in the derived contract by completing the function override.

Blockchain / Solidity

abstract contract Base {
    function doSomething() public virtual;
}

contract Derived is Base {
    function doSomething() public override [1];
}

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A{}

B;

C()

Dvirtual

Attempts:

3 left

💡 Hint

Common Mistakes

Ending the function with a semicolon instead of braces.

Omitting the function body.

When overriding an abstract function, you must provide a function body enclosed in curly braces {}.

4fill in blank

hard

Fill both blanks to declare an abstract contract with an abstract function and a state variable.

Blockchain / Solidity

abstract contract [1] {
    uint public [2];
    function doWork() public virtual;
}

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AWorker

Bvalue

Ccount

DTask

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid names for contract or variable.

Trying to assign a value to the abstract function.

The contract is named Worker and the state variable is value. Abstract functions have no body.

5fill in blank

hard

Fill all three blanks to implement a derived contract that overrides an abstract function and sets a state variable.

Blockchain / Solidity

abstract contract Base {
    uint public number;
    function setNumber(uint _num) public virtual;
}

contract Derived is Base {
    function [1](uint _num) public override {
        [2] = _num;
    }

    function getNumber() public view returns (uint) {
        return [3];
    }
}

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AsetNumber

Bnumber

DsetNum

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than the abstract function.

Using a wrong variable name inside the function.

The derived contract overrides setNumber to set the state variable number. The getter returns number.