Ether Payable – Running Smart Contracts When Receiving Ether Directly

etherpayable

I have a smart contract with a payable bet() function. When someone sends 1 ether to the bet function, the contract is executed.

I'd like the contract to run the same code when someone sends ether to the address explicitely (as if you're sending ether to someone else), without having to use the function bet().

How do I do this?

Thanks

Best Answer

you need to use the Fallback function like in the code below. this function is executed when someone send Ethers to the contract without providing any data or calling a function :

pragma solidity ^0.4.0;
contract bet{

    uint256 public bet;

    event received(string msg);

    function () payable{

        bet=msg.value;
        received("bet received");

    }


}

this function don't accept any parameters, you need when using this fallback to check your security model to avoid any problems.

Related Solutions

Solidity – Can Multiple Functions Be Payable?

payable is a modifier that allow a function to be called with a non zero value (that you can access via msg.value ) .

function canReceiveEther() payable {
 /// some code here
}

Exemple above will be able to be called and deal with any amount of ether sent to it .

If you do not mark your function as payable but someone do a call to it it will be rejected .

Now the function that you mentionned in your post is kinda a special one, it's what we call the fallback function (see the official doc here) That's the only function that can be unnamed and will be executed if you call the contract but none of the function match the parameters or if you don't provide data.

So in short :

More than one function can be marked as payable but only one can be the fallback function .
The fallback function will be called when :
- No functions match the data you provided .
- You call the contract with no data .
- You call the contract with send or transfer.

Note : fallback function only have access to a really limited amount of gas (2300 , see doc) . So it's better to keep the cost of the function as cheap as possible .

[Ethereum] function () public payable modifier can trigger actions when sending tokens or only works when sending ether

To be able to handle receiving tokens, you can make your class inherit from the ERC223Receiver standard:

contract ERC223Receiver
{
    function tokenFallback(address _from, uint _value, bytes _data);
}

contract YourContract is ERC223Receiver
{
    function tokenFallback(address _from, uint _value, bytes _data)
    {
        // Handle receiving tokens
    }
}

I have not tested this myself.

Source: https://github.com/ethereum/EIPs/issues/744

Best Answer

Related Solutions

Solidity – Can Multiple Functions Be Payable?

[Ethereum] function () public payable modifier can trigger actions when sending tokens or only works when sending ether

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