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Version: V3

Decrease Liquidity

Make sure to go through the Setting Up Your Contract before continuing to this section

Here we decrease the liquidity of our position without withdrawing all of it.

  • This example assumes the contract already has possession of the position NFT, and requires the calling address to be the same address that deposited the position NFT to our contract.

  • In production, amount0Min and amount1Min should be adjusted to create slippage protections.

Decrease Liquidity

    /// @notice A function that decreases the current liquidity by half. An example to show how to call the `decreaseLiquidity` function defined in periphery.
/// @param tokenId The id of the erc721 token
/// @return amount0 The amount received back in token0
/// @return amount1 The amount returned back in token1
function decreaseLiquidityInHalf(uint256 tokenId) external returns (uint256 amount0, uint256 amount1) {
// caller must be the owner of the NFT
require(msg.sender == deposits[tokenId].owner, 'Not the owner');
// get liquidity data for tokenId
uint128 liquidity = deposits[tokenId].liquidity;
uint128 halfLiquidity = liquidity / 2;

// amount0Min and amount1Min are price slippage checks
// if the amount received after burning is not greater than these minimums, transaction will fail
INonfungiblePositionManager.DecreaseLiquidityParams memory params =
INonfungiblePositionManager.DecreaseLiquidityParams({
tokenId: tokenId,
liquidity: halfLiquidity,
amount0Min: 0,
amount1Min: 0,
deadline: block.timestamp
});

(amount0, amount1) = nonfungiblePositionManager.decreaseLiquidity(params);

//send liquidity back to owner
_sendToOwner(tokenId, amount0, amount1);
}

Sending Fees To The Calling Address

This internal helper function sends any tokens, in the form of fees or position tokens, to the owner of an NFT.

In _sendToOwner, we pass the amount of fees due, previously populated in the last function, as arguments to safeTransfer, which transfers the fees to owner.

    /// @notice Transfers funds to owner of NFT
/// @param tokenId The id of the erc721
/// @param amount0 The amount of token0
/// @param amount1 The amount of token1
function _sendToOwner(
uint256 tokenId,
uint256 amount0,
uint256 amount1
) internal {
// get owner of contract
address owner = deposits[tokenId].owner;

address token0 = deposits[tokenId].token0;
address token1 = deposits[tokenId].token1;
// send collected fees to owner
TransferHelper.safeTransfer(token0, owner, amount0);
TransferHelper.safeTransfer(token1, owner, amount1);
}