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Version: 3.1.1

Unreal Engine Example

This is an example demonstrating how to make Meta Transactions inside Unreal Engine using this plugin.

Prepare Meta Transaction Data for the User to Sign​

Nonce​

First of all we want to get the user's nonce from the CounterForwarder contract that we deployed earlier.

Nonce

Data​

Save the encoded data of the incrementCounter function that we are going to call using a Meta Transaction.

Deadline​

In our case we will set the deadline to the current time plus 1 day from when the user signs the Meta Transaction in Unix Timestamp.

Data_Deadline

Private Key​

The user's private key that will be used to sign the Meta Transaction.

Domain​

The domain struct should contain:

  • Name: The name of the Forwarder that will be processing the transaction, in our case it is CounterForwarder.
  • Chain ID: The chain id of the Blockchain that the CounterForwarder contract is deployed on.
  • Verifying contract: This is the CounterForwarder contract address.

Message​

The message struct should contain:

  • From : The address of the user that will be signing this message.
  • To : The address of the deployed Counter contract.
  • Value : In our case it is 0 since the incrementCounter function is non-payable.
  • Gas : The gas limit that will be forwarded, we can set it to 300000.
  • Nonce : The user nonce that we received earlier.
  • Deadline : A Unix Timestamp after which the request is not executable anymore, which we calculated earlier.
  • Data : The encoded data of the incrementCounter function.

Sign Meta Transaction

Relayer Execution​

In our case we want a dedicated server to execute the Meta Transaction on behalf of a user.

Prepare Relayer Signing​

  • The server needs to receive the original Data that was used to create the Signed Meta Transaction.
  • First we will encode the data by selecting the execute function from the Forwarder contract ABI.
  • Then, we need to get the Relayer's nonce and the current gas price to execute the transaction.

Prepare Relayer

Relayer Signing and Sending​

  • After that we can call estimate gas function, so we can provide a gas limit to execute this transaction.
  • Then we can sign the transaction with the relayer's private key and provide all the needed arguments for the sign transaction function.
  • Lastly we can send this transaction to the Blockchain and the meta transaction will be executed.

Relayer Sign Send