Pair Addresses

getPair

The most obvious way to get the address for a pair is to call getPair on the factory. If the pair exists, this function will return its address, else address(0) (0x0000000000000000000000000000000000000000).

• The "canonical" way to determine whether or not a pair exists.
• Requires an onchain lookup.

CREATE2

Thanks to some fancy footwork in the factory, we can also compute pair addresses without any onchain lookups because of CREATE2. The following values are required for this technique:

• token0 must be strictly less than token1 by sort order.

• Can be computed offline.
• Requires the ability to perform keccak256.

Examples

Solidity

address factory = 0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f;
address token0 = 0xCAFE000000000000000000000000000000000000; // change me!
address token1 = 0xF00D000000000000000000000000000000000000; // change me!

address pair = address(uint160(bytes20(keccak256(abi.encodePacked(
  hex'ff',
  factory,
  keccak256(abi.encodePacked(token0, token1)),
  hex'96e8ac4277198ff8b6f785478aa9a39f403cb768dd02cbee326c3e7da348845f'
))));