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 on-chain lookup.

CREATE2

Thanks to some fancy footwork in the factory, we can also compute pair addresses without any on-chain lookups because of CREATE2. In Ring Swap, this is chain-aware: use the factory for the target network and the corresponding entry in INIT_CODE_HASH_MAP.

address	The factory address
salt	keccak256(abi.encodePacked(token0, token1))
keccak256(init_code)	INIT_CODE_HASH_MAP[chainId]

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

• Can be computed offline.
• Requires the ability to perform keccak256.
• In Ring Swap, token0 and token1 should be the actual pair tokens, which are often FewToken addresses rather than the original ERC-20 addresses shown to users.

Examples

Preferred SDK Method

For most applications, prefer the SDK helper rather than manual CREATE2:

import { ChainId, Token, WETH9 } from '@ring-protocol/sdk-core'
import { Pair, getFewTokenFromOriginalToken } from '@ring-protocol/v2-sdk'

const DAI = new Token(ChainId.MAINNET, '0x6B175474E89094C44Da98b954EedeAC495271d0F', 18, 'DAI', 'Dai Stablecoin')
const fewDAI = getFewTokenFromOriginalToken(DAI, ChainId.MAINNET)
const fewWETH = getFewTokenFromOriginalToken(WETH9[ChainId.MAINNET], ChainId.MAINNET)

const pairAddress = Pair.getAddress(fewDAI, fewWETH)

Manual TypeScript Example

This example makes use of the Ring V2 SDK. In practice, Pair.getAddress() is usually the safer option because it keeps your app aligned with the FEW-aware SDK behavior.

import { ChainId, Token, WETH9 } from '@ring-protocol/sdk-core'
import { FACTORY_ADDRESS_MAP, INIT_CODE_HASH_MAP, getFewTokenFromOriginalToken } from '@ring-protocol/v2-sdk'
import { pack, keccak256 } from '@ethersproject/solidity'
import { getCreate2Address } from '@ethersproject/address'

const chainId = ChainId.MAINNET
const DAI = new Token(chainId, '0x6B175474E89094C44Da98b954EedeAC495271d0F', 18, 'DAI', 'Dai Stablecoin')
const fewDAI = getFewTokenFromOriginalToken(DAI, chainId)
const fewWETH = getFewTokenFromOriginalToken(WETH9[chainId], chainId)
const [token0, token1] = fewDAI.sortsBefore(fewWETH) ? [fewDAI, fewWETH] : [fewWETH, fewDAI]

const pair = getCreate2Address(
  FACTORY_ADDRESS_MAP[chainId],
  keccak256(['bytes'], [pack(['address', 'address'], [token0.address, token1.address])]),
  INIT_CODE_HASH_MAP[chainId]
)