> ## Documentation Index
> Fetch the complete documentation index at: https://thrackle.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# ApplicationERC20UProxy

[Git Source](https://github.com/forte-service-company-ltd/forte-rules-engine/blob/6b9ac124d2cb0fe47a8b5c261a1dd458067f45ea/src/example/ERC20/upgradeable/ApplicationERC20UProxy.sol)

**Inherits:**
ERC1967Proxy

**Author:**
@ShaneDuncan602, @oscarsernarosero, @TJ-Everett

This is an example ERC721Proxy implementation that App Devs can use.

\*This contract implements a proxy that is upgradeable by an admin.
To avoid [https://medium.com/nomic-labs-blog/malicious-backdoors-in-ethereum-proxies-62629adf3357\[proxy](https://medium.com/nomic-labs-blog/malicious-backdoors-in-ethereum-proxies-62629adf3357\[proxy) selector
clashing], which can potentially be used in an attack, this contract uses the
[https://blog.openzeppelin.com/the-transparent-proxy-pattern/\[transparent](https://blog.openzeppelin.com/the-transparent-proxy-pattern/\[transparent) proxy pattern]. This pattern implies two
things that go hand in hand:

1. If any account other than the admin calls the proxy, the call will be forwarded to the implementation, even if
   that call matches one of the admin functions exposed by the proxy itself.
2. If the admin calls the proxy, it can access the admin functions, but its calls will never be forwarded to the
   implementation. If the admin tries to call a function on the implementation it will fail with an error that says
   "admin cannot fallback to proxy target".
   These properties mean that the admin account can only be used for admin actions like upgrading the proxy or changing
   the admin, so it's best if it's a dedicated account that is not used for anything else. This will avoid headaches due
   to sudden errors when trying to call a function from the proxy implementation.
   Our recommendation is for the dedicated account to be an instance of the {ProxyAdmin} contract. If set up this way,
   you should think of the `ProxyAdmin` instance as the real administrative interface of your proxy.\*

## Functions

### constructor

*Initializes an upgradeable proxy managed by `_admin`, backed by the implementation at `_logic`, and
optionally initialized with `_data` as explained in [ERC1967Proxy-constructor](/v1/reference/example/ERC20/ApplicationERC20.sol/contract.ApplicationERC20#constructor).*

```solidity
constructor(address _logic, address admin_, bytes memory _data) payable ERC1967Proxy(_logic, _data);
```

### ifAdmin

*Modifier used internally that will delegate the call to the implementation unless the sender is the admin.*

```solidity
modifier ifAdmin();
```

### admin

*Returns the current admin.
NOTE: Only the admin can call this function. See [ProxyAdmin-getProxyAdmin](https://docs.openzeppelin.com/contracts/4.x/api/proxy#ProxyAdmin).
TIP: To get this value clients can read directly from the storage slot shown below (specified by EIP1967) using the
[https://eth.wiki/json-rpc/API#eth\_getstorageat\[\`eth\_getStorageAt\`](https://eth.wiki/json-rpc/API#eth_getstorageat\[`eth_getStorageAt`)] RPC call.
`0xb53127684a568b3173ae13b9f8a6016e243e63b6e8ee1178d6a717850b5d6103`*

```solidity
function admin() external view ifAdmin returns (address admin_);
```

### implementation

*Returns the current implementation.
NOTE: Only the admin can call this function. See [ProxyAdmin-getProxyImplementation](https://docs.openzeppelin.com/contracts/4.x/api/proxy#ProxyAdmin-getProxyImplementation-contract-ITransparentUpgradeableProxy-).
TIP: To get this value clients can read directly from the storage slot shown below (specified by EIP1967) using the
[https://eth.wiki/json-rpc/API#eth\_getstorageat\[\`eth\_getStorageAt\`](https://eth.wiki/json-rpc/API#eth_getstorageat\[`eth_getStorageAt`)] RPC call.
`0x360894a13ba1a3210667c828492db98dca3e2076cc3735a920a3ca505d382bbc`*

```solidity
function implementation() external view ifAdmin returns (address implementation_);
```

### changeAdmin

*Changes the admin of the proxy.
Emits an {AdminChanged} event.
NOTE: Only the admin can call this function. See `{ProxyAdmin-changeProxyAdmin}`.*

```solidity
function changeAdmin(address newAdmin) external virtual ifAdmin;
```

### upgradeTo

*Upgrade the implementation of the proxy.
NOTE: Only the admin can call this function. See [ProxyAdmin-upgrade](https://docs.openzeppelin.com/contracts/4.x/api/proxy#ERC1967Upgrade-_upgradeTo-address-).*

```solidity
function upgradeTo(address newImplementation) external ifAdmin;
```

### upgradeToAndCall

*Upgrade the implementation of the proxy, and then call a function from the new implementation as specified
by `data`, which should be an encoded function call. This is useful to initialize new storage variables in the
proxied contract.
NOTE: Only the admin can call this function. See [ProxyAdmin-upgradeAndCall](https://docs.openzeppelin.com/contracts/4.x/api/proxy#ERC1967Upgrade-_upgradeToAndCall-address-bytes-bool-).*

```solidity
function upgradeToAndCall(address newImplementation, bytes calldata data) external payable ifAdmin;
```

### \_admin

*Returns the current admin.*

```solidity
function _admin() internal view virtual returns (address);
```

### \_beforeFallback

*Makes sure the admin cannot access the fallback function. See [Proxy-\_beforeFallback](https://docs.openzeppelin.com/contracts/4.x/api/proxy#Proxy-_beforeFallback--).*

```solidity
function _beforeFallback() internal virtual override;
```