此函数以原因字符串“ERC721：转移调用者不是所有者也不是批准”恢复

Question

Code:

function f(address nftContract, uint256 itemId, uint256 price) public payable nonReentrant 
{
  uint tokenId = idToMarketItem[itemId].tokenId;
  IERC721(nftContract).approve(address(this), tokenId);
  IERC721(nftContract).transferFrom(msg.sender, address(this), tokenId);
}

I really dont know whats wrong. Please help me

Answer 1

The fix is not to do the approve in your function:

function f(address nftContract, uint256 itemId, uint256 price) public payable nonReentrant 
{
  uint tokenId = idToMarketItem[itemId].tokenId;
  IERC721(nftContract).transferFrom(msg.sender, address(this), tokenId);
}

Because you are trying to have your contract approve itself to spend funds belonging to the caller (see the answer I linked in the comment, that explains why msg.sender is not what you think inside the IERC721(nftContract).approve call) this will not work. The user must directly call approve on the nftContract.

This is the user's nft, only it should have the right to approve their spending by a third party, no one else.