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Repo info
    Manoj Hulmani
    these tests look good
    but I have a problem with one mores test, which is supposed to fail, but passes!
           contract('Buy item', function() {
                          it("Buys item and tests the state", function() {
                              return amazon;
                               it("Adds item and tests", function() {
                                             console.log('State '+state);
    buyItem(1) cannot work!
    should not work!
    may be the contract is incorrect...
    but buyItem(0) and then getItem(0) should return a state and due to an incorrect comparsion should fail
    but it passes
    my updated contact is as follows:
    pragma solidity ^0.4.13;
    contract Amazon {
      /* set owner */
      address owner;
      /* Add a variable called skuCount to track the most recent sku # */
      uint private skuCount;
      /* Add a line that creates a public mapping that maps the SKU (a number) to an Item.
         Call this mappings items
      mapping (uint => Item) private items;
      /* Add a line that creates an enum called State. This should have 4 states
      enum State { ForSale, Sold, Shipped , Received }
      /* Create a struct named Item.
        Here, add a name, sku, price, state, seller, and buyer
        We've left you to figure out what the appropriate types are,
        if you need help you can ask around :)
      struct Item {
        string name;
        uint sku;
        uint price;
        State state;
        address seller;
        address buyer;
      /* Create 4 events with the same name as each possible State (see above)
        Each event should accept one argument, the sku*/
        event ForSale (uint skuCount);
        event Sold (uint sku, uint skuCount);
        event Shipped (uint sku);
        event Received (uint sku);
        event Send(uint sku);
        event GetItem(string item);
      modifier isOwner (address _owner) { require(msg.sender == _owner); _;}
      modifier isBuyer (address _owner) { require(msg.sender == _owner); _;}
      modifier paidEnough(uint _value) { require(_value <= msg.value); _;} //if the sku price <= the ether amount buyer has
      //refund them after pay for item (why it is before, _ checks for logic fo func) 
     //_amount should never be negative
     modifier checkValue(uint _amount) {  
        if (_amount > 0) {
      /* For each of the following modifiers, use what you learned about modifiers
       to give them functionality. For example, the forSale modifier should require
       that the item with the given sku has the state ForSale. */
      modifier forSale (uint _sku) { require(State.ForSale == items[_sku].state); _ ;}
      modifier sold (uint _sku) { require(State.Sold == items[_sku].state); _ ;}
      modifier shipped (uint _sku) { require(State.Shipped == items[_sku].state); _ ;}
      modifier received (uint _sku) { require(State.Received == items[_sku].state); _ ;}
      modifier validSkuValue (uint _sku) { require(_sku < skuCount); _ ;}    
      modifier notShipped (uint _sku) { require(State.Shipped != items[_sku].state); _ ;}
      modifier notReceived (uint _sku) { require(State.Received != items[_sku].state); _ ;}
      modifier notSold (uint _sku) { require(State.Sold != items[_sku].state); _ ;}
      function Amazon() {
        /* Here, set the owner as the person who instantiated the contract
           and set your skuCount to 0. */
           owner = msg.sender;
           skuCount = 0;
    function getSkuCount() returns (uint) {
        return skuCount;
    function getOwner() returns (address) {
        return owner;
     function getItem(uint sku) returns (string) {
        return items[sku].name;
    function getItemState(uint sku) returns (State) {
        return items[sku].state;
      function addItem(string _name, uint _price) {
        items[skuCount] = Item({name: _name, sku: skuCount, price: _price, state: State.ForSale, seller: msg.sender, buyer: msg.sender});
        skuCount = skuCount + 1;
      /* Add a keyword so the function can be paid. This function should transfer money
        to the seller, set the buyer as the person who called this transaction, and set the state
        to Sold. Be careful, this function should use 3 modifiers to check if the item is for sale,
        if the buyer paid enough, and check the value after the function is called to make sure the buyer is
        refunded any excess ether sent. Remember to call the event associated with this function!*/
      function buyItem(uint sku) payable
        items[sku].buyer = tx.origin; //transaction 

    if anyone can can give a clue about the mistake in this test case, it would be very helpful

    contract('Buy item', function() {
    it("Buys item and tests the state", function() {
    return amazon;
    it("Adds item and tests", function() {
    console.log('State '+state);


    Micah Dameron

    @Hulmani you have a question about Truffle's testing framework. Try asking your question in the ConsenSys/Truffle gitter, like so:

    Hulmani: Hey, I can't make sense out of the results of these truffle Tests. Why are they passing? I'm calling a non-existent function, so shouldn't they be failing?

    Writing the question shortly and concisely is more likely to get you an answer, and makes it so you don't have to send your whole contract into the chat prematurely. :)
    Nick Mudge
    I recently wrote EIP 173: Contract Ownership Standard: https://github.com/ethereum/EIPs/blob/master/EIPS/eip-173.md
    Looking for feedback about the standard here: ethereum/EIPs#173
    Manoj Hulmani
    @chronaeon while I appreciate you helping me out... I would like to point out that some people like me want context and samples... I am not sure how much questions you have asked and answered, I have seen so many ask for samples... so I like to be efficient and ask the question providing all the relevant information :smile: no offense...
    Micah Dameron
    Duly noted; thanks for the feedback
    Interested to know what the Truffle folks think of this issue
    Did you get a chance to ask in the Truffle channel?
    Does anyone know how to fix truffle compile if it isn't working on a OS device? I can't compile my smart contracts and its irking me.
    Manoj Hulmani
    @chronaeon Yes, I posted there before I posted here (cause I did not get a response for a while).... I used asyn/await to solve the issues, still struggling to find out how to solve without using aysn/await...
    Micah Dameron
    @tuckherin as an alternative compiler to Truffle, I recommend solc. Here's how to install it on a variety of devices.
    prapat polchan

    hello i deploy
    function deposit(uint256 amount) {

    // transfer the tokens from the sender to this contract
    balances[msg.sender] = balances[msg.sender].add(amount);
    ERC20(tracker_0x_address).transferFrom(msg.sender, this, amount);


    when call deposit remix alert

    Gas estimation errored with the following message (see below). The transaction execution will likely fail. Do you want to force sending?
    Error: gas required exceeds allowance or always failing transaction at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:1402159 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:932233 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:350777 at o (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:369008) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353607 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:350777 at c (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353883) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353921 at Ht (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:363290) at Object.<anonymous> (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:354010) at e.value (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:933148) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:932715 at n (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:368952) at o (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:369030) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353607 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:932681 at n (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:368952) at o (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:369030) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353607 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:933054 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:354417 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:350777 at c (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353883) at s (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353805) at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:353607 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:354397 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:932936 at chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:931373 at i (chrome-extension://nkbihfbeogaeaoehlefnkodbefgpgknn/background.js:1:1070602)

    Micah Dameron
    This error is being generated by MetaMask. Looks like someone started an issue about it here, but it hasn't been solved yet. Make sure to enter in your solution when you figure it out.
    Hey guys when i try to run truffle migrate i get this error
    Error encountered, bailing. Network state unknown. Review successful transactions manually.
    Error: Migrations contract constructor expected 1 arguments, received 0
    @MushroomMaula have you tried this option:
    truffle migrate --reset
    $ truffle init
    Error: Error making request to https://raw.githubusercontent.com/truffle-box/bar e-box/master/truffle.js. Got error: getaddrinfo ENOTFOUND raw.githubusercontent. com raw.githubusercontent.com:443. Please check the format of the requested reso urce.
    at Request._callback (C:\Users\blockchain\AppData\Roaming\npm\node_modules\t ruffle\build\webpack:~\truffle-box\lib\utils\unbox.js:45:1)
    at self.callback (C:\Users\blockchain\AppData\Roaming\npm\node_modules\truff le\build\webpack:~\request\request.js:185:1)
    at emitOne (events.js:116:13)
    at Request.emit (events.js:211:7)
    at Request.onRequestError (C:\Users\blockchain\AppData\Roaming\npm\node_modu les\truffle\build\webpack:~\request\request.js:877:1)
    at emitOne (events.js:116:13)
    at ClientRequest.emit (events.js:211:7)
    at TLSSocket.socketErrorListener (_http_client.js:387:9)
    at emitOne (events.js:116:13)
    at TLSSocket.emit (events.js:211:7)
    please give the instructions how to resolve it
    hello everyone im trying in my crowdsale to send back ether if someone bought above on the supply but it always revert because of transfer()
    if(receiveBGL > SALESUPPLY.sub(TokenSold)){
                //Calculation remaining tokens
                uint remainingTokens = SALESUPPLY.sub(TokenSold);
                emit LogDebug(remainingTokens);
                //Calculating price of token left
                uint tokenPriceInWei = remainingTokens.div(rate);
                emit LogDebug(tokenPriceInWei);
                //Calculation amount of wei to send back
                uint amountExceeds = weiPayment.sub(tokenPriceInWei);
                emit LogDebug(amountExceeds);
                //Sending back to recipient
                //Updating token that recipient will receive
                receive = remainingTokens;
    prapat polchan

    contract contractB {
    using SafeMath for uint256;
    address tracker_0x_address = 0x6b42FE821b653A0eae1a52249BF5cd58D1100890; // ContractA Address
    address to_address = 0xe459024A10b6Ed6189998706B8fd72fD0Dd00b97;
    mapping ( address => uint256 ) public balances;

    function sendTokens (uint256 amount) public
       //tokenAddress is the address of the ERC20 token deployed on Ropsten
        ERC20(tracker_0x_address).transfer(to_address, amount);


    this my contract
    why fail on call this function
    Micah Dameron
    @ManZerAirBow_twitter can you link the whole contract
    Affan Khan
    Hi, I need to write a solidity contract in which i can generate ethereum address and a function flush to send all addresses funds to destination address
    Hello everyone. I'm new to the blockchain technology. I wanted to learn the technical and development aspect of it. So how do I start? . Any sort of help would be appreciated. Thank you.
    Ben DiFrancesco
    Hey y’all, I have a smart contract with two public properties. One is an address and the other a uint. In my web3 front end, I almost always want to get both of these properties at the same time. I’ve implemented a get method in the contract that returns both properteis together, and I’m using this rather than declaring each property public. This makes accessing the data in my frontend easier, and actually requires about 1,000 less gas on deployment. Is there any downside to this approach that I’m missing?
    Adam Martin
    No issue that I know of.
    Hi, is it possible to deploy a token first, then deploy a separate contract at a later time for a public sale of the earlier deployed token?

    Hi I'm trying to create a crowdfund type contract whereby someone can create a 'mother' token and then go on to create child tokens that are forever attached to the mother.

    I had a little search and came up with the following code:

    import './Child.sol';
    mapping(bytes32 => Child) childList;
    mapping(bytes32 => Child) childList;
    function createMotherToken (address producer) public  {
        producer = msg.sender;
     function spawnChild(bytes32 childId) {
        Child current = new Child();
        childList[childId] = current;
    function callChildFunction(bytes32 childId) {


    Are there issues with this; and I'm assuming the import would go into my JS file? I am complete noob, so please go easy on me. Thanks for help..
    Vishal Waman


    We are using https://mainnet.infura.io/ with our Web3.js to listen events from Ethereum
    we receive almost 90% or events but 10% are never received

    Can anyone guide us on this ?


    Micah Dameron
    @apbendi , it's best to explicitly mark the visibility of your functions in callouts and state variables.
    @VishalWaman did you try the Infura gitter channel?
    Ben DiFrancesco
    Thanks @chronaeon , here’s my very simple contract. Note I have a public method for returning all contract state, as opposed to marking each property as public. Do you see a downside to this: https://github.com/apbendi/hodl_wallet/blob/master/contracts/HodlWallet.sol#L20
    @apbendi security wise, no downside. Possible downside is interoperability, ie. if other contracts want to get one or two values, they'll pay a bit more gas and have to handle the 4 return values. Cost of making all those values public is just a bit more bytecode to deploy.
    Ben DiFrancesco
    Thanks @maurelian, these all make sense. Just wanted to make sure I wasn’t missing anything else :)
    Hello, I have a smart contract and when trying to initialize it in a website, the address' for the token and token sale wont initialize, I am a newbie so any help will be appreciated! ( solidity, web3js )
    hi, I got this error message when I tried to truffle migrate my contracts to ropsten today
    Error encountered, bailing. Network state unknown. Review successful transactions manually. exceeds block gas limit
    anyone got this message ?
    I deployed successful few days ago