> For the complete documentation index, see [llms.txt](https://easonwang.gitbook.io/blockchain/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://easonwang.gitbook.io/blockchain/smart/openzeppelin-he-yao-library.md).

# OpenZeppelin 合約 library

引用其函式庫後快速產生 ERC-20 或 ERC-721、ERC-777、ERC-1155 等合約

{% embed url="<https://github.com/OpenZeppelin/openzeppelin-contracts>" %}

## 繼承方法

使用 is 繼承，之後可以使用其內的方法，直接呼叫。

<https://docs.openzeppelin.com/contracts/2.x/api/token/erc721>

```javascript
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/utils/Strings.sol";

contract Test is ERC721Enumerable, ReentrancyGuard, Ownable {
 ....
}

```

## 使用 Remix

![](https://3415061728-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M0u4DA5jITnh37VYXmj%2F-MZksWQNn8vkkHHUsPMz%2F-MZuDg4rUCWNfZLWygqO%2F%E6%88%AA%E5%9C%96%202021-05-05%20%E4%B8%8A%E5%8D%889.53.16.png?alt=media\&token=e4fb3c66-7ee0-4bec-b20f-0057d0b29c7e)

或是

![](https://3415061728-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M0u4DA5jITnh37VYXmj%2F-MZksWQNn8vkkHHUsPMz%2F-MZuDmEJMDfHRSLygdBu%2F%E6%88%AA%E5%9C%96%202021-05-05%20%E4%B8%8A%E5%8D%889.53.38.png?alt=media\&token=f8eb42ba-ebd2-4226-9aeb-d3bc9ff03fbc)

## Access control

可用來賦予不同的地址執行函數的權限。

{% embed url="<https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/access/AccessControl.sol>" %}

```javascript
contract token is ERC20, AccessControl {


    grantRole(DEFAULT_ADMIN_ROLE, msg.sender); // 讓 msg.sender 為 DEFAULT_ADMIN_ROLE 
    // _grantRole 的角色為 32byte sha3 算出來的，使用字串來產生 sha3 
    
    hasRole(bytes32 role, address account) // 確認地址擁有權限
  
    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
    // 使用 onlyRole 來限制某權限角色才可執行
f   function mint(address to, uint256 amount) public onlyRole(MINTER_ROLE) { 

    }
  }
}
```