Receiving Ether in Blockchain / Solidity - Step-by-Step Execution

Concept Flow - Receiving Ether

Contract deployed

↓

Send Ether to contract

↓

Fallback or receive function triggered?

Yes No↓

Accept Ether

↓

Update contract balance

When Ether is sent to a contract, the receive or fallback function runs to accept or reject the Ether, updating the contract's balance if accepted.

Execution Sample

Blockchain / Solidity

contract ReceiveEther {
    receive() external payable {
        // Accept Ether
    }
}

This contract accepts Ether sent to it by implementing the receive() function.

Execution Table

Step	Action	Condition	Function Triggered	Contract Balance Change	Result
1	Deploy contract	N/A	N/A	0 Ether	Contract ready to receive Ether
2	Send 5 Ether to contract	Ether sent with empty data	receive()	+5 Ether	Ether accepted
3	Send 3 Ether with data	Ether sent with data	fallback()	+3 Ether if fallback payable	Ether accepted if fallback payable, else rejected
4	Send 0 Ether call	No Ether sent	fallback()	0 Ether	No balance change
5	Send Ether but no receive or fallback payable	No payable function	None	0 Ether	Transaction rejected

💡 Execution stops when Ether is accepted or transaction is rejected due to no payable receive or fallback.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5
contract_balance	0 Ether	5 Ether	8 Ether (if fallback payable)	8 Ether	8 Ether

Key Moments - 3 Insights

Why does the receive() function trigger only when Ether is sent with empty data?

Because receive() is designed to handle plain Ether transfers without data, as shown in execution_table row 2 where Ether sent with empty data triggers receive().

What happens if Ether is sent with data but no payable fallback() exists?

The transaction is rejected, as shown in execution_table row 5 where no payable fallback or receive causes rejection.

Can the fallback() function accept Ether?

Yes, but only if it is marked payable. Otherwise, Ether sent with data will be rejected, as in execution_table rows 3 and 5.

Visual Quiz - 3 Questions

Look at the execution_table, which function is triggered when 5 Ether is sent with empty data?

A fallback()

B receive()

C constructor()

D no function

💡 Hint

Refer to execution_table row 2 under 'Function Triggered'

At which step does the contract balance increase by 3 Ether if fallback is payable?

A Step 3

B Step 2

C Step 4

D Step 5

💡 Hint

Check execution_table row 3 for balance change and function triggered

If the fallback function is not payable, what happens when Ether is sent with data?

A Ether accepted and balance updated

B receive() function triggered

C Transaction rejected

D Ether returned but balance updated

💡 Hint

See execution_table row 5 for no payable fallback scenario

Concept Snapshot

Receiving Ether in a contract:
- Use receive() external payable for plain Ether transfers
- Use fallback() external payable for calls with data
- Only payable functions accept Ether
- Contract balance updates when Ether accepted
- Transactions revert if no payable receive or fallback

Full Transcript

This visual execution trace shows how a smart contract receives Ether. When the contract is deployed, its balance starts at zero. Sending Ether with empty data triggers the receive() function, which accepts the Ether and increases the contract balance. Sending Ether with data triggers the fallback() function if it is payable; otherwise, the transaction is rejected. Sending calls without Ether triggers fallback() without balance change. If neither receive() nor fallback() is payable, any Ether sent causes rejection. Variables like contract_balance update accordingly after each step. Key moments clarify why receive() triggers only on empty data and the importance of payable fallback. The quiz tests understanding of which function triggers and what happens on payable or non-payable fallback. The snapshot summarizes the rules for receiving Ether in contracts.