Abstract contracts in Blockchain / Solidity - Mini Project: Build & Apply

Abstract Contracts in Solidity

📖 Scenario: You are building a simple blockchain-based system where different types of accounts share some common features but have their own specific behaviors. To organize your code well, you will use an abstract contract as a blueprint.

🎯 Goal: Create an abstract contract called Account with a function to get the account balance. Then, create a concrete contract called SavingsAccount that inherits from Account and implements the balance function. Finally, display the balance.

📋 What You'll Learn

Create an abstract contract named Account

Add an abstract function getBalance that returns a uint

Create a contract SavingsAccount that inherits from Account

Implement the getBalance function in SavingsAccount

Create a state variable balance in SavingsAccount initialized to 1000

Add a function to return the balance

Write a function to get the balance and print it

💡 Why This Matters

🌍 Real World

Abstract contracts help organize blockchain code by defining common interfaces for different types of accounts or contracts.

💼 Career

Understanding abstract contracts is important for blockchain developers to write clean, reusable, and maintainable smart contracts.

1

Create the abstract contract

Create an abstract contract called Account with an abstract function getBalance that returns a uint.

Blockchain / Solidity

// Create an abstract contract Account with an abstract function getBalance
// Your code here

Need a hint?

Use the abstract keyword before contract. Declare getBalance without a body and mark it virtual.

2

Create the concrete contract with balance

Create a contract called SavingsAccount that inherits from Account. Add a uint state variable called balance and set it to 1000.

Blockchain / Solidity

abstract contract Account {
    function getBalance() public view virtual returns (uint);
}

// Create contract SavingsAccount inheriting Account
// Add uint balance = 1000
// Your code here

Need a hint?

Use is Account to inherit. Declare balance as a state variable with initial value 1000.

3

Implement the abstract function

In SavingsAccount, implement the getBalance function to return the balance variable.

Blockchain / Solidity

abstract contract Account {
    function getBalance() public view virtual returns (uint);
}

contract SavingsAccount is Account {
    uint balance = 1000;

    // Implement getBalance to return balance
    // Your code here
}

Need a hint?

Use override keyword and return the balance variable.

4

Display the balance

Add a public function called showBalance in SavingsAccount that returns the result of getBalance(). Then, write a line to call showBalance() and print the returned balance.

Blockchain / Solidity

abstract contract Account {
    function getBalance() public view virtual returns (uint);
}

contract SavingsAccount is Account {
    uint balance = 1000;

    function getBalance() public view override returns (uint) {
        return balance;
    }

    // Add showBalance function that returns getBalance()
    // Your code here
}

// Call showBalance and print the result
// Your code here

Need a hint?

Create a public function that calls getBalance() and returns its value.