Multiple inheritance in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a contract that inherits from two contracts.

Blockchain / Solidity

contract MyContract is [1], ContractB {}

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AContractC

BMyContract

CBaseContract

DContractA

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to list the first parent contract.

Using the child contract name instead of a parent contract.

The contract MyContract inherits from ContractA and ContractB. You must list the parent contracts after is.

2fill in blank

medium

Complete the code to call the constructor of the first parent contract.

Blockchain / Solidity

contract MyContract is ContractA, ContractB {
    constructor() [1]() {}
}

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AContractA

Boverride

Csuper

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using super instead of the parent contract's name.

Omitting the parentheses after the contract name.

To call a parent contract's constructor explicitly, write its name followed by parentheses.

3fill in blank

hard

Fix the error in the function override declaration for multiple inheritance.

Blockchain / Solidity

function foo() public view virtual override([1]) returns (string memory) {
    return "Hello";
}

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AContractB

BContractA, ContractB

CContractA

DMyContract

Attempts:

3 left

💡 Hint

Common Mistakes

Listing only one parent contract in the override.

Using the child contract name in the override list.

When overriding a function from multiple parent contracts, list all parent contracts in the override keyword separated by commas.

4fill in blank

hard

Fill both blanks to define a contract that inherits and overrides a function from two parents.

Blockchain / Solidity

contract MyContract is [1], [2] {
    function foo() public view virtual override(ContractA, ContractB) returns (string memory) {
        return "Hello from MyContract";
    }
}

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AContractA

BMyContract

CContractB

DBaseContract

Attempts:

3 left

💡 Hint

Common Mistakes

Using the child contract name in the inheritance list.

Forgetting to list both parent contracts.

The contract inherits from ContractA and ContractB. The function foo overrides the versions from both parents.

5fill in blank

hard

Fill all three blanks to create a mapping with keys from one contract and values from another.

Blockchain / Solidity

mapping([1] => [2]) public data;

function setData([3] key, uint value) public {
    data[key] = value;
}

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Aaddress

Buint

Dstring

Attempts:

3 left

💡 Hint

Common Mistakes

Using mismatched types for mapping keys and function parameters.

Using string instead of address for keys.

The mapping uses address as keys and uint as values. The function parameter key is of type address.