Factory pattern in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a new contract instance using the factory.

Blockchain / Solidity

contract MyFactory {
    function create() public returns (address) {
        [1] newContract = new SimpleContract();
        return address(newContract);
    }
}

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

ASimpleContract

BFactory

CContract

DInstance

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong contract name that does not exist.

Trying to return the contract type instead of its address.

The factory creates a new instance of SimpleContract using the new keyword.

2fill in blank

medium

Complete the code to store the address of the created contract in the factory.

Blockchain / Solidity

contract MyFactory {
    address[] public contracts;

    function create() public {
        SimpleContract newContract = new SimpleContract();
        contracts.[1](address(newContract));
    }
}

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Ainsert

Bpush

Cremove

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop which removes elements instead of adding.

Trying to assign directly without using array methods.

The push method adds the new contract address to the contracts array.

3fill in blank

hard

Fix the error in the factory function to correctly emit an event after contract creation.

Blockchain / Solidity

contract MyFactory {
    event ContractCreated(address contractAddress);

    function create() public {
        SimpleContract newContract = new SimpleContract();
        emit [1](address(newContract));
    }
}

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AContractCreatedEvent

BCreatedContract

CContractCreated

DNewContract

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong event name that does not exist.

Misspelling the event name or changing its case.

The event declared is ContractCreated, so it must be emitted with that exact name.

4fill in blank

hard

Fill both blanks to define a factory that creates different contract types based on input.

Blockchain / Solidity

contract Factory {
    function create(uint8 typeId) public returns (address) {
        if (typeId == 1) {
            return address(new ContractA());
        } else if (typeId == 2) {
            return address(new [1]());
        } else {
            revert("Invalid type");
        }
    }
}

contract ContractA {}
contract [2] {}

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AContractB

BContractC

CContractA

DFactory

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the contract creation and definition.

Trying to create a contract that is not defined.

The factory creates ContractB when typeId is 2, so both blanks must be ContractB.

5fill in blank

hard

Fill all three blanks to implement a factory that creates contracts with an owner and stores them.

Blockchain / Solidity

contract Owned {
    address public owner;
    constructor(address _owner) {
        owner = _owner;
    }
}

contract Factory {
    address[] public contracts;

    function create(address _owner) public returns (address) {
        Owned newContract = new Owned([1]);
        contracts.[2](address(newContract));
        emit Created([3]);
        return address(newContract);
    }

    event Created(address contractAddress);
}

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A_owner

Bpush

Caddress(newContract)

Downer

Attempts:

3 left

💡 Hint

Common Mistakes

Passing wrong argument to the constructor.

Using wrong array method instead of push.

Emitting wrong value in the event.

The constructor needs _owner as argument, the contract address is pushed to the array, and the event emits the new contract's address.