CallGaslessFunction

This is an advanced feature and can drain user wallet funds if you interact with a malicious contract. Only link to trusted smart contract authors.
Description
This function behaves similar to the CallGenericWriteFunction, however it allows your users to make transactions without paying Gas Fees - the gas fees is instead borne by you, the developer. This is useful for users new to crypto or new to your game, since they do not need to own or purchase crypto before making transactions in your game, which reduces player churn. 
Metafi follows the ERC2771 Standard for relaying gasless transactions. For more information on the gasless transaction standard, please refer to the official EIPS Docs.
Details
Implementation Details
When you create an API key, a Relayer wallet will be created for you across your supported chains, which you will need to fund with crypto that will be used to pay the user gas fees. You can find the public wallet address in your project settings page. Additionally, you will need to perform the following steps.
1.Make your smart contract ERC2771 compatible. You can do this by inheriting from Metafi's ERC2771Context contract that can be found here (This is based on OpenZeppelin's ERC2771Context contract, however allows for updating the list of trusted forwarders in the future)
2.For the functions that you would like to use Gasless transactions on, replace  msg.sender() statements in your contract with _msgSender(), and msg.data() with _msgData() as per the EIPS docs linked above.
3.Register Metafi's Forwarder Contracts as a trusted forwarder address. You can do this by calling the setTrustedForwarder function in the ERC2771Context contract with Metafi's forwarder addresses that have been shown below.
Metafi Forwarder Addresses
Chain
Forwarder Contract Address
Ethereum Mainnet
TBD
Goerli
0x04f1e3E36667e747DB9878c2c677E291DD942701
Matic Mainnet
TBD
Matic Mumbai
0xD7aD34eEbDE6cB057A11F3f824260799961Ab01a
Signature
async CallGasslessFunction(args, apiKey)
Arguments
Parameter
Type
Definition
args.callback?
Function
Function to callback upon getting result from the smart contract function call

For numerical return values, please refer to the section below.

Structure of result object passed into callback function:
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{
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    "status": 1/0, // success or fail
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    "data": "data", // the transaction object
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    "error": "error", // error string if any
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}
args.contractAddress
String
Contract address of the smart contract to be called
args.functionABI
JSON
The JSON object for the smart contract ABI​
args.functionName
String
Name of the function to be called
args.value?
BigNumber
The value to be sent along with the smart contract invocation. Please refer to the section below for more information.
args.chain
chain (class)
Which chain to broadcast the transaction on. Pick a chain from the supported chains list​
args.params
array
Array of objects that will be sent as the arguments to the smart contract function. Please ensure that the order of params matches the contract ABI.

For large numerical inputs, please refer to the section below.
apiKey
String
The API Key generated from the Developer Portal​
Return Value
None
Handling Large Numerical Values
Applicable to EVM Chains only
While passing in large numerical values (values above 9007199254740991) in args.params, a conversion to BigNumber format needs to be made. You can use the following methods that convert the number to and from the appropriate format:
ConvertNumberToBigNumber(number, decimal) - Use this method while passing in numbers as params to a smart function that requires uint256 numbers
ConvertBigNumberToNumber(bigNumber, decimal) - Use this method while converting response values from a smart contract function call (which are in bigNumber format) to a JS Number
Example
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import stakeContractAbi from './contracts/abi/stakeContract.json'
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import {
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    CallGaslessFunction,
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    ConvertNumberToBigNumber,
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    chains
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} from '@metafi/metafi-js-package';
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​
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function App() {
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    const stakeTokensGasless = () => {
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        CallGaslessFunction({
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                chain: chains.eth,             
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                contractAddress: "0xF5C9F957705bea56a7e806943f98F7877B995826",   
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                functionABI: stakeContractAbi.abi,   
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                functionName: "stake",
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                value: ConvertNumberToBigNumber(1, 18),
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                params: [],
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                callback: (res) => {
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                    console.log(res);
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                }
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            },
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            "YOUR-API-KEY"
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        );
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    }
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    return (
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        <div>
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	    <button onClick={stakeTokensGasless}>stakeTokensGasless</button>
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        </div>
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    );
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}
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​
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export default App;
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​

Chain	Forwarder Contract Address
Ethereum Mainnet	TBD
Goerli	`0x04f1e3E36667e747DB9878c2c677E291DD942701`
Matic Mainnet	TBD
Matic Mumbai	`0xD7aD34eEbDE6cB057A11F3f824260799961Ab01a`

Parameter	Type	Definition
`args.callback?`	Function	Function to callback upon getting result from the smart contract function call For numerical return values, please refer to the section below. Structure of result object passed into callback function: 1 { 2 "status": 1/0, // success or fail 3 "data": "data", // the transaction object 4 "error": "error", // error string if any 5 }
`args.contractAddress`	String	Contract address of the smart contract to be called
`args.functionABI`	JSON	The JSON object for the smart contract ABI
`args.functionName`	String	Name of the function to be called
`args.value?`	BigNumber	The value to be sent along with the smart contract invocation. Please refer to the section below for more information.
`args.chain`	chain (class)	Which chain to broadcast the transaction on. Pick a chain from the supported chains list
`args.params`	array	Array of objects that will be sent as the arguments to the smart contract function. Please ensure that the order of params matches the contract ABI. For large numerical inputs, please refer to the section below.
`apiKey`	String	The API Key generated from the Developer Portal

CallGenericWriteFunctionTest

RetrieveUser

Last modified 3mo ago