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Simple logic event with firing in function, work perfectly as expected in truffle develop console, but never firing on my Dapp created with create-react-app, it's just seems to not listen/monitor the network, I've people saying it should continuously load POST request to monitor network, but not in my case. I use Metamask, and all smart-contract function calls works fine on react, except events.

event RoundStarted(uint256 closingBlock);

function roundStart() public ownerOnly {
    RoundStarted(block.number + ROUND_LENGTH);
}

And the line of code I used in truffle develop console, which is not working when I paste it in componentWillMount()

  Loto.deployed().then(function(instance){
    return instance.RoundStarted({},{fromBlock: 0, toBlock: 'latest'});
  }).then((result) => {
    return result.watch((error,result) => { 
      console.log('Found him!')
    })
  })

UPD: I found out that events works fine in truffle react box, so this kinda solves the problem, but I still don't know how did they manage it, it's not my code problem, something about dependencies, I'd like to know what do I miss in my create-react-app.

  • To get a reference to the Loto contract are you doing something similar to this const Loto = Contract(LotoContract); Loto.setProvider(web3.currentProvider)? Where web3 is from the injected provider eg MetaMask. – willjgriff Jan 28 '18 at 10:49
  • @willjgriff, Yep, exactly, but I use truffle-contract and json file to get contract, like this: import { default as contract } from 'truffle-contract' import loto_artifacts from './Loto.json' var Loto = contract(loto_artifacts); Loto.setProvider(web3.currentProvider); Again, I think problem more like in react or something between them, I tried web3 0.20.4 and 1.0.0-29beta, both works for functions and everything but not events. – Andrew Katsewich Jan 28 '18 at 13:45
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Does it work if you remove all of the JS object arguments in the contract event call, eg if you replace line 2 in your snippet with return instance.RoundStarted();

I haven't experimented with specifying start and end blocks that I want to monitor within but perhaps specifying the end block as 'latest' takes the latest block at the time your componentWillMount() function is called which is likely a block before your event is fired.

  • Yep, I was trying it without args in a first time, and I saw someone suggest to use them which helped to someone, so I tried both ways, and I tried to call an event watcher in componentWillMount() as well as in componentDidMount() simultaneously, and separately, and on button click, so I think it's not were the problem is, need to go deeper. – Andrew Katsewich Jan 29 '18 at 10:22

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