The OKTC SwapFactory contract is a foundational component of the decentralized exchange (DEX) infrastructure on the OKTC blockchain. It enables the creation and management of trading pairs for tokens, forming the backbone of automated market maker (AMM) functionality. This guide provides a comprehensive breakdown of the contract’s structure, read and write functions, emitted events, and key operational mechanics—all while maintaining clarity for developers and blockchain enthusiasts.
Whether you're building on OKTC or integrating with existing liquidity pools, understanding the SwapFactory contract is essential for interacting with decentralized trading ecosystems.
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Understanding the SwapFactory Contract
Contract Name: SwapFactory
Contract Address: 0x7b9F0a56cA7D20A44f603C03C6f45Db95b31e539
Source Code: SwapFactory.sol on GitHub
Explorer Link: View Factory Contract on Oklink
The SwapFactory contract acts as a registry and deployment hub for token pairs. When two tokens need to be traded against each other, this contract checks if a pair already exists or creates a new one using deterministic address generation. It also tracks global parameters such as fee distribution and governance controls.
Core keywords: OKTC, SwapFactory, decentralized exchange, liquidity pool, smart contract, token pair, AMM, fee distribution
Read Functions: Querying Contract State
These functions allow users and developers to retrieve critical data from the SwapFactory without altering the blockchain state.
getHash()
function getHash() public pure returns(bytes32)Returns the creation code hash of the SwapPair contract. This value is used internally to compute the deterministic address of any new pair, ensuring predictability and security in pair deployment.
This function is pure, meaning it doesn’t interact with storage and consumes no gas when called off-chain.
getPair(address tokenA, address tokenB)
function getPair(address tokenA, address tokenB) external view returns (address pair)Returns the address of the trading pair for two given tokens. The order of tokenA and tokenB does not matter—the function automatically sorts them to maintain consistency.
If no pair exists, it returns the zero address (0x00...00). This is useful for checking whether liquidity has already been created between two assets.
allPairs(uint index)
function allPairs(uint) external view returns (address pair)Retrieves the address of the pair at a specific index (0-based). This allows iteration over all created pairs, which can be valuable for analytics tools or front-end interfaces listing available markets.
For non-existent indices, it returns the zero address.
allPairsLength()
function allPairsLength() external view returns (uint)Returns the total number of trading pairs currently deployed via this factory. This counter increments every time a new pair is created and serves as a metric for platform growth and liquidity coverage.
feeTo()
function feeTo() external view returns (address)Indicates the wallet or contract address where protocol-level fees (if enabled) are collected. These fees typically come from a portion of swap fees not distributed to liquidity providers.
feeToSetter()
function feeToSetter() external view returns (address)Returns the address authorized to update the feeTo address. This introduces a governance mechanism, allowing only designated entities to redirect fee collection—a critical security feature.
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Write Functions: Modifying Contract Behavior
These functions change the contract state and require transaction execution.
createPair(address tokenA, address tokenB)
function createPair(address tokenA, address tokenB) external returns (address pair)Deploys a new trading pair for two ERC-20 tokens if one doesn’t already exist. The function uses sorted token addresses to ensure only one unique pair per token combination.
Upon successful deployment, it emits the PairCreated event and increments the pair counter. This is typically the first step in establishing liquidity for a new token.
Important: Both tokens must be valid ERC-20 contracts, and neither can be the zero address.
setFeeTo(address)
function setFeeTo(address) externalUpdates the destination address for protocol fees. Only callable by the current feeToSetter, this function allows dynamic control over revenue streams—useful for treasury management or community-owned protocols.
setFeeToSetter(address)
function setFeeToSetter(address) externalTransfers authority to update the feeTo address to another account. Often used during decentralization phases where control moves from a single entity to a DAO or multi-sig wallet.
Events: Tracking On-Chain Activity
Events provide transparency and enable off-chain systems to monitor contract activity.
PairCreated
event PairCreated(address indexed token0, address indexed token1, address pair, uint)Emitted whenever a new trading pair is deployed. Includes:
token0: The first token in sorted order.token1: The second token.pair: The newly created contract address.uint: The sequential ID of the pair (starts at 1).
Indexing token0 and token1 allows efficient filtering by specific tokens using blockchain explorers or event listeners.
Interface Overview
The SwapFactory implements a standard interface compatible with common DEX tooling and developer libraries. While the full interface isn’t detailed here, it aligns with conventional AMM factory patterns seen in Uniswap V2-style implementations—making integration familiar for experienced developers.
Frequently Asked Questions
Q: Can anyone create a trading pair on OKTC using SwapFactory?
A: Yes—any user can call createPair for any two ERC-20 tokens, provided no pair already exists. There are no permission restrictions on pair creation, promoting open market access.
Q: How is the address of a new pair determined?
A: The pair address is computed using a deterministic method based on the factory address, sorted token addresses, and the SwapPair creation code hash (getHash). This allows prediction of addresses before deployment.
Q: Who controls fee collection in the SwapFactory?
A: The feeToSetter has exclusive rights to change the feeTo address. Initially set to a deployer-controlled wallet, this can later be transferred to enhance decentralization.
Q: Are there fees taken by the protocol on swaps?
A: While liquidity providers earn most swap fees, a small portion may be routed to the feeTo address if enabled. The current configuration depends on governance decisions reflected in the contract state.
Q: How can I track all active trading pairs?
A: Use allPairsLength() to get the total count, then loop through indices with allPairs(n) to retrieve each pair address. Alternatively, listen for PairCreated events in real time.
Q: Is the SwapFactory upgradeable?
A: No—the current implementation appears immutable. However, future versions could introduce proxy patterns if governance evolves toward upgradability.
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By mastering the SwapFactory contract, developers gain foundational knowledge for building liquidity-driven applications on OKTC. From launching new markets to analyzing fee flows, this contract empowers decentralized innovation across DeFi use cases.