Convert

Convert.sol

pragma solidity ^0.4.21;

contract Convert {
    
    address owner;
    address public fromContractAddr;
    address public toContractAddr;
    
    mapping (uint => bool) public isConvert;
    
    modifier onlyOwner {
        require(msg.sender == owner);
        _;
    }
    
    function Convert() public {
        owner = msg.sender;
    }
    
    function setFromContractAddr(address _addr) public onlyOwner {
        fromContractAddr = _addr;
    }
    
    function setToContractAddr(address _addr) public onlyOwner {
        toContractAddr = _addr;
    }
    
    function getNewToken(uint _tokenId) public {
        IFrom ifrom = IFrom(fromContractAddr);
        require(ifrom.ownerOf(_tokenId) == msg.sender);
        require(isConvert[_tokenId] == false);
        
        isConvert[_tokenId] = true;
        
        ITo ito = ITo(toContractAddr);
        ito.issueTokenAndTransfer(1, msg.sender);
    }
    
    // 721token拥有者已经协商好，把各自的某个token相互交换。
    
    // _tokenId_1是ifrom合约里面的，_tokenId_2是ito合约里面的
    function approveToken(uint _tokenId_1, uint _tokenId_2) public {
        IFrom ifrom = IFrom(fromContractAddr);
        ITo ito = ITo(toContractAddr);
        
        address ownerOfToken1 = ifrom.ownerOf(_tokenId_1);
        address ownerOfToken2 = ito.ownerOf(_tokenId_2);
        
        require(msg.sender == ownerOfToken1);
        
        ifrom.approve(this, _tokenId_1);
        
        if (ito.approvedFor(_tokenId_2) == this) {
            ito.transferFrom(ownerOfToken2, ownerOfToken1, _tokenId_2);
            ifrom.transferFrom(ownerOfToken1, ownerOfToken2, _tokenId_1);
        }
                
    
    /* only read */
    
}

interface IFrom {
    function ownerOf (uint256 _itemId) public view returns (address _owner);
    function approve(address _to, uint256 _tokenId) public;
    function transferFrom(address _from, address _to, uint256 _tokenId);    

}

interface ITo {
    function issueTokenAndTransfer(uint256 _count, address to) public;
    function approvedFor(uint256 _tokenId) public view returns (address _approved);
    function transferFrom(address _from, address _to, uint256 _tokenId) public;

}