# Factory

## Code

[`UniswapV2Factory.sol`](https://github.com/Uniswap/uniswap-v2-core/blob/master/contracts/UniswapV2Factory.sol)

## Address

`UniswapV2Factory` is deployed at `0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f` on the Ethereum [mainnet](https://etherscan.io/address/0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f), and the [Ropsten](https://ropsten.etherscan.io/address/0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f), [Rinkeby](https://rinkeby.etherscan.io/address/0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f), [Görli](https://goerli.etherscan.io/address/0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f), and [Kovan](https://kovan.etherscan.io/address/0x5C69bEe701ef814a2B6a3EDD4B1652CB9cc5aA6f) testnets. It was built from commit [8160750](https://github.com/Uniswap/uniswap-v2-core/tree/816075049f811f1b061bca81d5d040b96f4c07eb).

## Events

### PairCreated

```solidity
event PairCreated(address indexed token0, address indexed token1, address pair, uint);
```

Emitted each time a pair is created via [createPair](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

* `token0` is guaranteed to be strictly less than `token1` by sort order.
* The final `uint` log value will be `1` for the first pair created, `2` for the second, etc. (see [allPairs](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference)/[getPair](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference)).

## Read-Only Functions

### getPair

```solidity
function getPair(address tokenA, address tokenB) external view returns (address pair);
```

Returns the address of the pair for `tokenA` and `tokenB`, if it has been created, else `address(0)` (`0x0000000000000000000000000000000000000000`).

* `tokenA` and `tokenB` are interchangeable.
* Pair addresses can also be calculated deterministically, see Pair Addresses.

### allPairs

```solidity
function allPairs(uint) external view returns (address pair);
```

Returns the address of the `n`th pair (`0`-indexed) created through the factory, or `address(0)` (`0x0000000000000000000000000000000000000000`) if not enough pairs have been created yet.

* Pass `0` for the address of the first pair created, `1` for the second, etc.

### allPairsLength

```solidity
function allPairsLength() external view returns (uint);
```

Returns the total number of pairs created through the factory so far.

### feeTo

```solidity
function feeTo() external view returns (address);
```

See Protocol Charge Calculation.

### feeToSetter

```solidity
function feeToSetter() external view returns (address);
```

The address allowed to change [feeTo](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

## State-Changing Functions

### createPair

```solidity
function createPair(address tokenA, address tokenB) external returns (address pair);
```

Creates a pair for `tokenA` and `tokenB` if one doesn't exist already.

* `tokenA` and `tokenB` are interchangeable.
* Emits [PairCreated](https://docs.quickswap.exchange/technical-reference/smart-contracts/v2/broken-reference).

## Interface

```solidity
import '@uniswap/v2-core/contracts/interfaces/IUniswapV2Factory.sol';
```

```solidity
pragma solidity >=0.5.0;

interface IUniswapV2Factory {
  event PairCreated(address indexed token0, address indexed token1, address pair, uint);

  function getPair(address tokenA, address tokenB) external view returns (address pair);
  function allPairs(uint) external view returns (address pair);
  function allPairsLength() external view returns (uint);

  function feeTo() external view returns (address);
  function feeToSetter() external view returns (address);

  function createPair(address tokenA, address tokenB) external returns (address pair);
}
```

## ABI

```typescript
import IUniswapV2Factory from '@uniswap/v2-core/build/IUniswapV2Factory.json'
```

<https://unpkg.com/@uniswap/v2-core@1.0.0/build/IUniswapV2Factory.json>