有没有办法检查ERC721代币被铸造了多少次

Question

我使用的是OpenZeppelin的ERC721库，有没有一种方法可以计算代币的铸造次数。

有没有内置的映射或函数来检查这一点？

Answer 1

您可以使用Enumerable扩展。totalSupply()函数返回当前存在的令牌数量(铸造的减去燃烧的(，在某些情况下，这可能与铸造的令牌总量不同。

pragma solidity ^0.8;
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Burnable.sol";
/*
* `totalSupply()` (defined in ERC721Enumerable) returns 1
* even though 2 tokens were minted, but 1 was also burned
*/
contract MyCollection is ERC721Enumerable, ERC721Burnable {
constructor() ERC721("CollectionName", "Symbol") {
_mint(msg.sender, 1);
_burn(1);
_mint(msg.sender, 2);
}
// multiple parents define the same function
// overriding here just to point at the expected parent class
// related to the combination of `Burnable` and `Enumerable` in the same contract - not to `Enumerable` alone
function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal override(ERC721, ERC721Enumerable) {
return ERC721Enumerable._beforeTokenTransfer(from, to, tokenId);
}
// same reason for overriding as above
function supportsInterface(bytes4 interfaceId) public view override(ERC721, ERC721Enumerable) returns (bool) {
return ERC721Enumerable.supportsInterface(interfaceId);
}
}

或者，您可以覆盖_beforeTokenTransfer()挂钩并创建一个只考虑铸造而忽略烧录的自定义计数器。

pragma solidity ^0.8;
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Burnable.sol";
/*
* `mintCounter` returns 2, ignores the burned tokens
*/
contract MyCollection is ERC721Enumerable, ERC721Burnable {
uint256 public mintCounter;
constructor() ERC721("CollectionName", "Symbol") {
_mint(msg.sender, 1);
_burn(1);
_mint(msg.sender, 2);
}
function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal override(ERC721, ERC721Enumerable) {
if (from == address(0)) {
mintCounter++;
}
return ERC721Enumerable._beforeTokenTransfer(from, to, tokenId);
}
function supportsInterface(bytes4 interfaceId) public view override(ERC721, ERC721Enumerable) returns (bool) {
return ERC721Enumerable.supportsInterface(interfaceId);
}
}