Cross-chain bridges in Blockchain / Solidity - Mini Project: Build & Apply

Cross-chain Bridges Basics

📖 Scenario: You are building a simple program to track token transfers between two blockchains using a cross-chain bridge. This helps users move tokens safely from one chain to another.

🎯 Goal: Create a program that stores token balances on two chains, sets a minimum transfer amount, processes transfers only if they meet the minimum, and shows the updated balances.

📋 What You'll Learn

Create a dictionary called chain_balances with exact keys 'ChainA' and 'ChainB' and initial balances 1000 and 500 respectively

Create a variable called min_transfer and set it to 100

Write a function called transfer_tokens that takes amount and transfers tokens from 'ChainA' to 'ChainB' only if amount is greater than or equal to min_transfer

Print the updated chain_balances after a transfer of 150 tokens

💡 Why This Matters

🌍 Real World

Cross-chain bridges let users move tokens between different blockchains, enabling more flexible and powerful blockchain applications.

💼 Career

Understanding how to track and control token transfers across chains is important for blockchain developers working on decentralized finance (DeFi) and interoperability solutions.

1

Set up initial chain balances

Create a dictionary called chain_balances with keys 'ChainA' and 'ChainB' having values 1000 and 500 respectively.

Blockchain / Solidity

# Create the chain_balances dictionary with initial values
# Your code here

Need a hint?

Use curly braces {} to create a dictionary with the given keys and values.

2

Set minimum transfer amount

Create a variable called min_transfer and set it to 100.

Blockchain / Solidity

chain_balances = {'ChainA': 1000, 'ChainB': 500}
# Set the minimum transfer amount
# Your code here

Need a hint?

Just assign the number 100 to the variable min_transfer.

3

Write transfer function

Write a function called transfer_tokens that takes a parameter amount. Inside the function, check if amount is greater than or equal to min_transfer. If yes, subtract amount from chain_balances['ChainA'] and add it to chain_balances['ChainB']. If not, do nothing.

Blockchain / Solidity

chain_balances = {'ChainA': 1000, 'ChainB': 500}
min_transfer = 100
# Define the transfer_tokens function below
# Your code here

Need a hint?

Use def to create the function and an if statement to check the amount.

4

Perform transfer and show balances

Call the function transfer_tokens with 150 as the argument. Then print the chain_balances dictionary to show updated balances.

Blockchain / Solidity

chain_balances = {'ChainA': 1000, 'ChainB': 500}
min_transfer = 100

def transfer_tokens(amount):
    if amount >= min_transfer:
        chain_balances['ChainA'] -= amount
        chain_balances['ChainB'] += amount

# Call transfer_tokens with 150 and print chain_balances
# Your code here

Need a hint?

Call the function with 150 and then print the dictionary to see the new balances.