adapters.md

Adapters

Adapters are contracts that can hook into the normal flow of cross-chain transactions and augment their capabilities without requiring changes in existing contracts. The connext/integration repository contains adapters that can be inherited for these purposes.

SwapAdapter

This adapter contains the logic for swapping tokens. The SwapAdapter can be used on either the origin or the destination side to execute a swap.

Using on Origin

SwapAndXCall is a contract that implements SwapAdapter and is meant to be used on the origin chain. It swaps the input tokens into desired output tokens before initiating the cross-chain transaction with xcall. This is useful in cases where you want users to be able to send any token to your contract and bridge them through Connext.

Using on Destination

SwapForwarderXReceiver also implements SwapAdapter but it's used on the destination chain. It swaps the tokens received from the bridge into desired output tokens before proceeding with the "forward call", which contains the rest of the logic that follows on the destination side. The ForwarderXReceiver that it implements is detailed in the next section for Receivers.

Swappers

The SwapAdapter holds a registry of allowedSwappers which are contracts that implement the ISwapper interface:

interface ISwapper {
  function swap(
    uint256 _amountIn,
    address _tokenIn,
    address _tokenOut,
    bytes calldata _swapData
  ) external payable returns (uint256 amountOut);
}

For example, the UniV3Swapper implements swap which internally calls Uniswap's ISwapRouter.exactInputSingle to execute the swap via Uniswap.

Currently, Connext provides the following Swappers:

• OneInchUniswapV3
• UniV2Swapper
• UniV3Swapper