Receiving Ether in Blockchain / Solidity - Mini Project: Build & Apply

Receiving Ether

📖 Scenario: You want to create a simple smart contract on the Ethereum blockchain that can receive Ether payments. This contract will hold the Ether sent to it and allow you to check its balance.

🎯 Goal: Build a Solidity smart contract that can receive Ether and keep track of the total Ether it has received.

📋 What You'll Learn

Create a contract named ReceiveEther

Add a receive function to accept Ether

Add a public function getBalance that returns the contract's Ether balance

💡 Why This Matters

🌍 Real World

Smart contracts often need to accept payments or donations in Ether. This project shows the simplest way to do that.

💼 Career

Understanding how to receive and manage Ether is essential for blockchain developers working on decentralized finance (DeFi) or payment systems.

1

Create the contract skeleton

Write a Solidity contract named ReceiveEther with the correct version pragma pragma solidity ^0.8.0;.

Blockchain / Solidity

pragma solidity ^0.8.0;

// Create contract ReceiveEther
contract ReceiveEther {
    
    // Your code here
}

Hint

Start by declaring the Solidity version and the contract name.

2

Add the receive function

Inside the ReceiveEther contract, add a receive external payable function to accept Ether transfers.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract ReceiveEther {
    
    // Add receive function to accept Ether
    receive() external payable {
        // Your code here
    }
}

Hint

The receive function has no name and no arguments. It must be marked external and payable.

3

Add a function to get contract balance

Add a public view function named getBalance that returns the contract's current Ether balance as uint.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract ReceiveEther {
    receive() external payable {
        // This function is intentionally left blank to accept Ether
    }

    // Add getBalance function to return contract balance
    function getBalance() public view returns (uint) {
        // Your code here
    }
}

Hint

Use address(this).balance to get the contract's Ether balance.

4

Test the contract output

Write a comment showing how to call getBalance() to check the contract's Ether balance.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract ReceiveEther {
    receive() external payable {
        // This function is intentionally left blank to accept Ether
    }

    function getBalance() public view returns (uint) {
        return address(this).balance;
    }
}

// Call getBalance() to see the contract's Ether balance
// Your code here

Hint

Show a comment with example code calling getBalance().

Practice

1.

What is the main purpose of the receive function in a Solidity contract?

easy

A. To reject incoming Ether transfers

B. To send Ether from the contract to an external address

C. To initialize contract state variables

D. To accept Ether sent to the contract without any data

Solution

1. Step 1: Understand the role of the receive function

   The receive function is a special function in Solidity that is triggered when the contract receives Ether without any calldata.

2. Step 2: Identify its purpose

   Its purpose is to accept Ether sent directly to the contract without any function call data.

3. Final Answer:

   To accept Ether sent to the contract without any data -> Option D

4. Quick Check:

   receive function = accept Ether without data [OK]

Hint: Remember: receive handles plain Ether transfers only [OK]

Common Mistakes:

• Confusing receive with fallback function
• Thinking receive sends Ether out
• Assuming receive initializes variables

2.

Which of the following is the correct syntax for a receive function in Solidity?

?

easy

A. receive() internal payable {}

B. receive() external payable {}

C. receive() external {}

D. receive() public payable {}

Solution

1. Step 1: Recall receive function requirements

   The receive function must be declared as external and payable to accept Ether without data.

2. Step 2: Match syntax

   receive() external payable {} matches the required syntax: receive() external payable {}.

3. Final Answer:

   receive() external payable {} -> Option B

4. Quick Check:

   receive must be external and payable [OK]

Hint: receive must be external and payable, no public or internal [OK]

Common Mistakes:

• Using public instead of external
• Omitting payable keyword
• Making receive internal or private

3.

Consider this Solidity contract snippet:

contract Test {
    event Received(address sender, uint amount);
    receive() external payable {
        emit Received(msg.sender, msg.value);
    }
}

What happens when someone sends 1 Ether to this contract without calling any function?

medium

A. The contract rejects the Ether and transaction fails

B. The contract accepts Ether but does not emit any event

C. The contract accepts the Ether and emits the Received event

D. The contract calls fallback function instead

Solution

1. Step 1: Analyze the receive function

   The receive function is payable and emits an event with sender and amount when Ether is received without data.

2. Step 2: Understand the behavior on Ether transfer

   Sending 1 Ether without data triggers receive, so Ether is accepted and event emitted.

3. Final Answer:

   The contract accepts the Ether and emits the Received event -> Option C

4. Quick Check:

   receive payable + emit event = accept and notify [OK]

Hint: Sending Ether without data triggers receive, not fallback [OK]

Common Mistakes:

• Thinking fallback is called instead
• Assuming no event is emitted
• Believing Ether is rejected

4.

Identify the error in this Solidity contract snippet that prevents it from receiving Ether:

contract Example {
    receive() public payable {
        // code
    }
}

medium

A. receive function must be external, not public

B. receive function must not be payable

C. receive function must have a return type

D. receive function must be internal

Solution

1. Step 1: Check receive function visibility

   The receive function must be declared as external, not public.

2. Step 2: Confirm payable requirement

   It is correctly marked payable, so no error there.

3. Final Answer:

   receive function must be external, not public -> Option A

4. Quick Check:

   receive must be external, not public [OK]

Hint: receive must be external, not public or internal [OK]

Common Mistakes:

• Using public instead of external
• Removing payable keyword
• Adding return type to receive

5.

You want to create a contract that tracks the total Ether received and rejects any Ether sent with data. Which combination of functions should you implement?

hard

A. Implement receive() external payable to accept Ether and fallback() external to revert on data

B. Implement only fallback() external payable to accept all Ether

C. Implement receive() external without payable and fallback() external payable

D. Implement receive() external payable and fallback() external payable both accepting Ether

Solution

1. Step 1: Accept Ether without data using receive

   The receive function accepts Ether sent without data and can update total received.

2. Step 2: Reject Ether sent with data using fallback

   The fallback function should revert to reject any Ether sent with data.

3. Final Answer:

   Implement receive() external payable to accept Ether and fallback() external to revert on data -> Option A

4. Quick Check:

   receive accepts plain Ether, fallback rejects data [OK]

Hint: Use receive for plain Ether, fallback to reject data [OK]

Common Mistakes:

• Making fallback payable and accepting Ether with data
• Omitting fallback to reject data
• Not marking receive payable