...essage);
return a % b;
}
}
/**
* @dev Interface of the ERC20 standard as defined in the EIP.
*/
interface IERC20Upgradeable {
/**
* @dev Returns the amount of tokens in existence.
*/
function totalSupply() external view returns (uint256);
/**
...
... virtual {
_transfer(from, to, tokenId);
require(_checkOnERC721Received(from, to, tokenId, _data), "ERC721: transfer to non ERC721Receiver implementer");
}
````
先执行了_transfer函数后执行_checkOnERC721Received函数,而后者是为了检测to这个参数是否...