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@openzeppelin/contracts-upgradeable
Advanced tools
@openzeppelin/contracts-upgradeable is a library for secure smart contract development. It provides reusable and upgradeable smart contract components that follow best practices in security and gas efficiency. The package is particularly useful for creating upgradeable smart contracts, which can be modified after deployment without changing their address.
Upgradeable Contracts
This feature allows you to create upgradeable contracts using the Initializable base contract. The `initialize` function is used instead of a constructor to set initial values.
```json
{
"code": "import { Initializable } from '@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol';\n\ncontract MyContract is Initializable {\n uint256 public value;\n\n function initialize(uint256 _value) public initializer {\n value = _value;\n }\n}"}
```
Access Control
This feature provides role-based access control mechanisms. The `AccessControlUpgradeable` contract allows you to define roles and restrict access to certain functions based on these roles.
```json
{
"code": "import { AccessControlUpgradeable } from '@openzeppelin/contracts-upgradeable/access/AccessControlUpgradeable.sol';\n\ncontract MyAccessControl is Initializable, AccessControlUpgradeable {\n bytes32 public constant ADMIN_ROLE = keccak256('ADMIN_ROLE');\n\n function initialize(address admin) public initializer {\n _setupRole(ADMIN_ROLE, admin);\n }\n}"}
```
ERC20 Token
This feature allows you to create upgradeable ERC20 tokens. The `ERC20Upgradeable` contract provides the standard ERC20 functionality, and the `initialize` function sets the token's name and symbol.
```json
{
"code": "import { ERC20Upgradeable } from '@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol';\n\ncontract MyToken is Initializable, ERC20Upgradeable {\n function initialize(string memory name, string memory symbol) public initializer {\n __ERC20_init(name, symbol);\n }\n}"}
```
zos-lib is a library for writing upgradeable smart contracts. It provides similar functionalities to @openzeppelin/contracts-upgradeable, including initializable contracts and upgradeable proxies. However, it is less actively maintained compared to @openzeppelin/contracts-upgradeable.
Truffle is a development environment, testing framework, and asset pipeline for Ethereum. While it does not focus solely on upgradeable contracts, it provides tools for managing smart contract development and deployment, including migrations which can be used to handle upgrades.
Hardhat is a development environment for Ethereum software. It offers a flexible and extensible way to manage smart contract development and testing. While it does not provide built-in support for upgradeable contracts, it can be used in conjunction with other libraries like @openzeppelin/contracts-upgradeable to achieve similar functionality.
A library for secure smart contract development. Build on a solid foundation of community-vetted code.
:mage: Not sure how to get started? Check out Contracts Wizard — an interactive smart contract generator.
:building_construction: Want to scale your decentralized application? Check out OpenZeppelin Defender — a secure platform for automating and monitoring your operations.
Note You are looking at the upgradeable variant of OpenZeppelin Contracts. Be sure to review the documentation on Using OpenZeppelin Contracts with Upgrades.
$ npm install @openzeppelin/contracts-upgradeable
OpenZeppelin Contracts features a stable API, which means that your contracts won't break unexpectedly when upgrading to a newer minor version.
An alternative to npm is to use the GitHub repository (openzeppelin/openzeppelin-contracts-upgradeable
) to retrieve the contracts. When doing this, make sure to specify the tag for a release such as v4.5.0
, instead of using the master
branch.
Once installed, you can use the contracts in the library by importing them:
pragma solidity ^0.8.0;
import "@openzeppelin/contracts-upgradeable/token/ERC721/ERC721Upgradeable.sol";
contract MyCollectible is ERC721Upgradeable {
function initialize() initializer public {
__ERC721_init("MyCollectible", "MCO");
}
}
If you're new to smart contract development, head to Developing Smart Contracts to learn about creating a new project and compiling your contracts.
To keep your system secure, you should always use the installed code as-is, and neither copy-paste it from online sources nor modify it yourself. The library is designed so that only the contracts and functions you use are deployed, so you don't need to worry about it needlessly increasing gas costs.
The guides in the documentation site will teach about different concepts, and how to use the related contracts that OpenZeppelin Contracts provides:
The full API is also thoroughly documented, and serves as a great reference when developing your smart contract application. You can also ask for help or follow Contracts's development in the community forum.
Finally, you may want to take a look at the guides on our blog, which cover several common use cases and good practices. The following articles provide great background reading, though please note that some of the referenced tools have changed, as the tooling in the ecosystem continues to rapidly evolve.
This project is maintained by OpenZeppelin with the goal of providing a secure and reliable library of smart contract components for the ecosystem. We address security through risk management in various areas such as engineering and open source best practices, scoping and API design, multi-layered review processes, and incident response preparedness.
The security policy is detailed in SECURITY.md
, and specifies how you can report security vulnerabilities, which versions will receive security patches, and how to stay informed about them. We run a bug bounty program on Immunefi to reward the responsible disclosure of vulnerabilities.
The engineering guidelines we follow to promote project quality can be found in GUIDELINES.md
.
Past audits can be found in audits/
.
Smart contracts are a nascent technology and carry a high level of technical risk and uncertainty. Although OpenZeppelin is well known for its security audits, using OpenZeppelin Contracts is not a substitute for a security audit.
OpenZeppelin Contracts is made available under the MIT License, which disclaims all warranties in relation to the project and which limits the liability of those that contribute and maintain the project, including OpenZeppelin. As set out further in the Terms, you acknowledge that you are solely responsible for any use of OpenZeppelin Contracts and you assume all risks associated with any such use.
OpenZeppelin Contracts exists thanks to its contributors. There are many ways you can participate and help build high quality software. Check out the contribution guide!
OpenZeppelin Contracts is released under the MIT License.
Your use of this Project is governed by the terms found at www.openzeppelin.com/tos (the "Terms").
4.9.0 (2023-05-23)
ReentrancyGuard
: Add a _reentrancyGuardEntered
function to expose the guard status. (#3714)ERC721Wrapper
: add a new extension of the ERC721
token which wraps an underlying token. Deposit and withdraw guarantee that the ownership of each token is backed by a corresponding underlying token with the same identifier. (#3863)EnumerableMap
: add a keys()
function that returns an array containing all the keys. (#3920)Governor
: add a public cancel(uint256)
function. (#3983)Governor
: Enable timestamp operation for blockchains without a stable block time. This is achieved by connecting a Governor's internal clock to match a voting token's EIP-6372 interface. (#3934)Strings
: add equal
method. (#3774)IERC5313
: Add an interface for EIP-5313 that is now final. (#4013)IERC4906
: Add an interface for ERC-4906 that is now Final. (#4012)StorageSlot
: Add support for string
and bytes
. (#4008)Votes
, ERC20Votes
, ERC721Votes
: support timestamp checkpointing using EIP-6372. (#3934)ERC4626
: Add mitigation to the inflation attack through virtual shares and assets. (#3979)Strings
: add toString
method for signed integers. (#3773)ERC20Wrapper
: Make the underlying
variable private and add a public accessor. (#4029)EIP712
: add EIP-5267 support for better domain discovery. (#3969)AccessControlDefaultAdminRules
: Add an extension of AccessControl
with additional security rules for the DEFAULT_ADMIN_ROLE
. (#4009)SignatureChecker
: Add isValidERC1271SignatureNow
for checking a signature directly against a smart contract using ERC-1271. (#3932)SafeERC20
: Add a forceApprove
function to improve compatibility with tokens behaving like USDT. (#4067)ERC1967Upgrade
: removed contract-wide oz-upgrades-unsafe-allow delegatecall
annotation, replaced by granular annotation in UUPSUpgradeable
. (#3971)ERC20Wrapper
: self wrapping and deposit by the wrapper itself are now explicitly forbidden. (#4100)ECDSA
: optimize bytes32 computation by using assembly instead of abi.encodePacked
. (#3853)ERC721URIStorage
: Emit ERC-4906 MetadataUpdate
in _setTokenURI
. (#4012)ShortStrings
: Added a library for handling short strings in a gas efficient way, with fallback to storage for longer strings. (#4023)SignatureChecker
: Allow return data length greater than 32 from EIP-1271 signers. (#4038)UUPSUpgradeable
: added granular oz-upgrades-unsafe-allow-reachable
annotation to improve upgrade safety checks on latest version of the Upgrades Plugins (starting with @openzeppelin/upgrades-core@1.21.0
). (#3971)Initializable
: optimize _disableInitializers
by using !=
instead of <
. (#3787)Ownable2Step
: make acceptOwnership
public virtual to enable usecases that require overriding it. (#3960)UUPSUpgradeable.sol
: Change visibility to the functions upgradeTo
and upgradeToAndCall
from external
to public
. (#3959)TimelockController
: Add the CallSalt
event to emit on operation schedule. (#4001)Math
: optimize log256
rounding check. (#3745)ERC20Votes
: optimize by using unchecked arithmetic. (#3748)Multicall
: annotate multicall
function as upgrade safe to not raise a flag for its delegatecall. (#3961)ERC20Pausable
, ERC721Pausable
, ERC1155Pausable
: Add note regarding missing public pausing functionality (#4007)ECDSA
: Add a function toDataWithIntendedValidatorHash
that encodes data with version 0x00 following EIP-191. (#4063)MerkleProof
: optimize by using unchecked arithmetic. (#3745)EIP712
: Addition of ERC5267 support requires support for user defined value types, which was released in Solidity version 0.8.8. This requires a pragma change from ^0.8.0
to ^0.8.8
.EIP712
: Optimization of the cache for the upgradeable version affects the way name
and version
are set. This is no longer done through an initializer, and is instead part of the implementation's constructor. As a consequence, all proxies using the same implementation will necessarily share the same name
and version
. Additionally, an implementation upgrade risks changing the EIP712 domain unless the same name
and version
are used when deploying the new implementation contract.ERC20Permit
: Added the file IERC20Permit.sol
and ERC20Permit.sol
and deprecated draft-IERC20Permit.sol
and draft-ERC20Permit.sol
since EIP-2612 is no longer a Draft. Developers are encouraged to update their imports. (#3793)Timers
: The Timers
library is now deprecated and will be removed in the next major release. (#4062)ERC777
: The ERC777
token standard is no longer supported by OpenZeppelin. Our implementation is now deprecated and will be removed in the next major release. The corresponding standard interfaces remain available. (#4066)ERC1820Implementer
: The ERC1820
pseudo-introspection mechanism is no longer supported by OpenZeppelin. Our implementation is now deprecated and will be removed in the next major release. The corresponding standard interfaces remain available. (#4066)FAQs
Secure Smart Contract library for Solidity
The npm package @openzeppelin/contracts-upgradeable receives a total of 177,485 weekly downloads. As such, @openzeppelin/contracts-upgradeable popularity was classified as popular.
We found that @openzeppelin/contracts-upgradeable demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 4 open source maintainers collaborating on the project.
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