contract xyz {
    mapping(address => bool) Users;
    function add(address userAddress) {
            require(userAddress != 0x0 && !Users[userAddress]);             
            Users[userAddress] = true;    
    function pass(address passAddress) returns (bool) {   
        return Users[passAddress];

contract SaveData {
    address[] addrs;
    string[] hashSet;
    xyz asd = xyz();
    function Save(address PubAddress) {
        addrs.push(PubAddress);    //saving public addresses

//function to save hash
    function saveHash(string hashStr) {

I am new to solidity, i am creating a simple user reg and checking and saving it using another contract. Contract xyz is working fine, but now i want to call it into SaveData Contract and check address using pass function that if address is whitelisted then only it will save the address.

thanks in advance

  • 1
    Possible duplicate of Call function on another contract Dec 19 '17 at 6:40
  • @MichaelKohl what i need is that i have deployed my xyz contract and it generating an address. Now i need to send the same address in savedata contract and save it using save function. Dec 19 '17 at 6:56
  • This looks fine, except you are never calling asd.add() to whitelist your addresses. What are you finding is not working? (also, no need for "==true" in your require.) Dec 19 '17 at 13:27

The main thing is you cast a variable as an instance of your contract, then you instantiate it at the address where you expect it to be.

Something like

MyContract myContract; 
myContract = MyContract(contractAddress);

I couldn't help myself and adjusted the names of some things.

pragma solidity 0.4.21;

contract UserReg {

    mapping(address => bool) public isUser;

    function add(address userAddress) public {
        require(userAddress != 0x0 && !isUser[userAddress]);             
        isUser[userAddress] = true;    

    function pass(address passAddress) public view returns(bool) {   
        return isUser[passAddress];

    // Added this for safety check near 31

    function isUserReg() public pure returns(bool isIndeed) {
        return true;

contract SaveData {

    address[] public addrs;

    UserReg userReg;

    function instantiateXyz(address userRegAddr) public returns(bool success) {
        userReg = UserReg(userRegAddr);     // instantiate asd instance of Zyz
        require(userReg.isUserReg());       // should return true, right?
        return true;

    function saveAddress(address pubAddress) public returns(bool success) {
        addrs.push(pubAddress);    //saving public addresses
        return true;


Hope it helps.


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