Cross-chain bridges in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to initialize a bridge connection to Ethereum network.

Blockchain / Solidity

const bridge = new Bridge({ network: '[1]' });

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ASolana

BEthereum

CPolkadot

DBitcoin

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a network other than Ethereum will cause connection failure.

The bridge must connect to the Ethereum network, so 'Ethereum' is the correct choice.

2fill in blank

medium

Complete the code to lock tokens on the source chain before bridging.

Blockchain / Solidity

await bridge.lockTokens('[1]', amount);

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AsourceAddress

Brecipient

CtokenAddress

DdestinationAddress

Attempts:

3 left

💡 Hint

Common Mistakes

Using destination or recipient address instead of source address.

Tokens must be locked from the source address before bridging.

3fill in blank

hard

Fix the error in the code to correctly verify the bridge transaction hash.

Blockchain / Solidity

const isValid = await bridge.verifyTransaction('[1]');

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AblockNumber

Btransaction

CtxHash

Dreceipt

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the whole transaction object or block number instead of txHash.

The verification function requires the transaction hash (txHash) to confirm the transaction.

4fill in blank

hard

Fill both blanks to create a mapping of token symbols to their bridge contract addresses.

Blockchain / Solidity

const tokenBridgeMap = { '[1]': '[2]' };

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AUSDT

B0x123abc456def7890

CDAI

D0xabcdef1234567890

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping keys and values or using wrong token symbols.

The token symbol 'USDT' maps to its bridge contract address '0x123abc456def7890'.

5fill in blank

hard

Fill all three blanks to filter tokens with balance greater than zero and map their symbols to balances.

Blockchain / Solidity

const positiveBalances = { [1]: balances[[2]] for [3] in balances if balances[[3]] > 0 };

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Atoken

Damount

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently in comprehension.

We use 'token' as the variable name to iterate keys and check balances.