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Version: 0.2.x-amarok

Nested xCalls

Cross-chain calls can easily be composed together by xcalling within the xReceive function of a target contract. In effect, the target contract becomes the source contract of that nested xcall.

xCall in xReceive‚Äč

contract Target is IXReceiver {
function xReceive(
bytes32 _transferId,
uint256 _amount,
address _asset,
address _originSender,
uint32 _origin,
bytes memory _callData
) external returns (bytes memory) {
// After handling the first xcall...
...

// Send another xcall within the xReceive function!
connext.xcall{value: relayerFee}(...);
}
}

There are many ways to use nested xcalls to extend cross-chain functionality. With this technique, it's possible to:

  • Emulate the behavior of a "callback" between chains to verify state changes and/or followup asynchronously
  • Disperse data to multiple different chains at once

See this in action in the Ping Pong example.