Questions tagged [events]

Solidity events and logging problems. Events allow the convenient usage of the EVM logging facilities, which in turn can be used to “call” JavaScript callbacks in the user interface of a dapp, which listen for these events.

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Viewing transaction events by using web3 on geth console

According to https://web3py.readthedocs.io/en/stable/contracts.html#web3.contract.ContractEvents.myEvent web3 allows to extract the pertinent logs from a transaction receipt: tx_hash = contract....
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469 views

How to listen contract event in Python

The test contract is pragma solidity ^0.5.0; contract Test{ event Here(uint256 indexed a); uint256 public a; function add() public returns (uint256){ a += 1; emit Here(...
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Can events always be called directly by user accounts? Is there a way to make them internal?

I am using events to fire an order, basically using them as a vehicle for a master/slave connection with an IoT device, through the blockchain. Ideally i want to always verify the right msg.sender is ...
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49 views

Mapping or indexed event

I want to store data on chain that is not needed within a smart contract but should be retrieved easily and particularly quickly from outside. I know that storing the data within an indexed event is ...
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55 views

getting the latest holders address:balance for a smart contract

I managed to get all the transfer events from any given smart contract, but now I need to reduce that to current holder any idea how I would do this? Here is my code so far: import ERC20ABI from './...
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Truffle Exec Return Events

I have set up a JavaScript file that takes in my contract and executes the various functions and then returns the correct events. The file runs through 'truffle exec'. I am using the following line ...
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1answer
342 views

Web3.js event.get not firing, whereas event.watch gives correct values

I am trying to do a simple test for events. Following is solidity code. Values received from chgEvent.watch are always correct. But in chgEvent.get, results1 is empty. chgEvent.get does not get ...
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2answers
270 views

Solidity event function not appearing in web3

I have a contract with the following event (using 0.4.24): event UpdateProgress(bool _gameInProgress); I am registering the contract like this: import Web3 from 'web3'; import address from './...
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2answers
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Subscribing to multiple Transfer events of various ERC20s

I need to suscribe to Transfer events of couple of different ERC20s in order to catch transfers to my contract. And here is the question: to catch all those events I need to create instance of each ...
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1answer
58 views

Problem watching events without invoke functions in the Smart Contract

I have an event which is sent each time when a contract is deployed. It is launched in the constructor. I have a Dapp where I want to watch this event to send a tx each time that a smart contract is ...
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How to read ALL logs of a certain event

When I read event logs like this: myContract.getPastEvents('myEventLogName', { fromBlock: 0, toBlock: 'latest' }) .then(function(events){ console.log(events) // same results as the ...
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1answer
823 views

Proper way of using allEvents()

I'm trying to get all events for a contract: let events = token.allEvents({fromBlock: creationBlock, toBlock: 'latest'}, (err, res) => { try { let result = events.get(); ...
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can't read past event logs

const event = contractInst.Transfer({},{fromBlock: 0, toBlock: 'latest'}); events.get(function (error, result) { if (!error) { console.log(result); } }); The get ...
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Listen to filtered events using web3js 0.19 (provided by infura)

I am working on a uport dApp. uPort by default uses web3 from rinkeby.infura.io which is web3 version 0.19. So no WebSocket available. I tried ZeroClientProvider but that leads to this error: Error ...
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Events firing but bool variable not changing in value

Given a contract with an event as follows contract test { event LogEvent( address a, bool result ); function testInputs(some parameters) public (){ .... ...
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160 views

Unable to catch contract event using parity websockets

I have a contract deployed on ropsten which emits event when ether amount is deposited in it. I can see the event appearing in etherscan. this.web3Socket = new Web3(new Web3.providers....
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When exactly do events fire

I have a web3J application that is supposed to deploy a contract (by calling a function on another contract) then listen for the contractCreatedEvent that is fired by the factoryContract and then call ...
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1k views

How to use events to retrieve data from a transaction? PRIVATE CHAIN

i am using GETH for the architecture and deployment of my contract on a private chain and it works pretty fine, but unfortunately i want to return data from a transaction function and this makes me ...
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1answer
391 views

Why myContract.events.MyEvent([options][, callback]) does not return “data” and “logs”?

We have an event as follows : event LogNewObject(address sender, bytes32 indexed id, bytes32 sub_states_types, bytes32 sub_states_values, address owner); This event is called in following function : ...
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1answer
61 views

A common error at time of using web3 options

When i use some web3 options as follows, I receive a common error i.e. TypeError: web3.[option] is not a function For example : TypeError: web3.toAscii is not a function web3.toAscii(...
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826 views

Truffle Test Sell Event Assertion Error

When I test my selling event in truffle.So, the following error comes:- The solidity code is :- event Sell(address _buyer, uint256 _amount); // Buy token function buyTokens(uint256 _numberOfTokens) ...
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677 views

Listen to emitted event from front-end

Could somebody please provide me code that works to listen to an event from your front-end. It was working for me and there are a few tutorials that I've tried now to fix it but it still persists with ...
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1answer
331 views

How to prevent callback event occur twice?

Hi this is my web3 code events.watch(function (error,result){ if (error) { console.log('Error:'+JSON.stringify(error)); res.send({'status':0,'message':...
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157 views

Testrpc some times not returning event after transaction execution

I am using testrpc to test my contract While executing some functions in my contract I have observed some inconstancy in responses from testrpc, Same function call give me 3 different results at ...
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81 views

Indexed event parameter only returns 1st character in address

pragma solidity ^0.4.13; contract OwnedI { /** * Event emitted when a new owner has been set. * @param previousOwner The previous owner, who happened to effect the change. * @param ...
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1answer
167 views

How do I watch Events from multiple contracts

I wrote a script that is able to read events from one contract address and then paste it into a .csv. Now I would like to extend that script listening watching/reading the same event of several ...
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1answer
88 views

Can not see Solidity events

I can see events in a private net, but when I connect to "real" net, I can not see them. Meaning .watch(function(err, result) is never called. My theory is I am using lightning, and it probably means ...
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2answers
607 views

Events with string argument not working (not indexed)

I am trying to listen to an event on rinkeby test which I run locally. Every thing works fine when my argument is int such as event EventTester(int values); When I change the event argument to string ...
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Using events and logs to get function returned value with a simple example

My question is related to this one: Can a contract function both change the state and return a value when it's called externally Question: How to read event/log content? I have a contract like:...
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1answer
147 views

Watching for events returns 0 blocknumber

I am trying to listen for recently mined events from a live smartcontract(EtherDelta). //https://github.com/praneethmendu/ethualizer/blob/master/backnd.js tradeEvent = contractIns.Trade({}...
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1answer
500 views

Simple event watching with testrpc - unexpected output

Working with this example, I've been attempting to utilise event watching from the web js api. Window 1 (a testrpc instance with filled account): testrpc -a 1 Window 2 geth attach rpc:http://...
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717 views

Regarding Event Generation Cost

Lets say events are invoked from all the methods of a contract. Each event is storing some data. The methods where only computation or data fetching logic is applied will it cost ether if any event is ...
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2answers
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ERC-20 without events

I have created a non-compliant ERC-20 token that does not emit any events. I do not want to fix this bug, because fixing it produces other troubles. So, an ERC-20 token with this bug (not emitting ...
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1answer
71 views

Capture Solidity Emit Events without Web3 — E.g., Calling via Postman

Is there some way to capture Solidity Emit Events without the use of Web3? For example, I am calling via Postman JSON RPC eth_sendTransaction. How to capture the returned results?

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