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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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2answers
67 views

Different events for revert types or one event and then on the client/backend figure the reason why it reverted from emitted data?

Let's say I have 3 conditions which can lead to revert(). which way should I handle it? 3 types of events or one event with extra parameters? 3 events types: if condition A: emit causeA(dataA1, ...
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0answers
41 views

Trying and failing to switch my dapp from local node to infura, please help? [closed]

I have a nodejs 'server' running that listens for events on the blockchain. Currently I have this line in my code: var provider = new Web3.providers.HttpProvider("http://localhost:8545"); But I'm ...
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1answer
61 views

Infura event listening [duplicate]

I am using Infura, Ropsten Test network, Web3@0.20 in the back-end of my Express website. I want to listen events in my ERC20 contract. I tried a lot of methods, but still failed. How do I revise it? ...
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1answer
165 views

How to get EVENT name from event signature hash?

I fount that some developers can get event_signature_hash for a event's name MyEvent(uint256) by using bellow code: event_signature_hash = w3.sha3(text='MyEvent(uint256)').hex() But vice versa, I ...
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1answer
79 views

Why do my events not emit the correct value?

When testing a contract with Truffle, I have found that the variables that are emitted by the event do not match the values that are passed into the event emission. Why does the event not return the ...
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0answers
14 views

How can I use the parameters of an event as a function input?

how can I use the indexed parameter of a triggered event as a input for a function called in response to that event triggered? This is the event: event LogOfferAccepted( uint _id, ...
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3answers
4k views

Indexed Event with string not getting logged

I am facing a strange issue in my solidity smart contract using events. I created the event in 2 ways as below:- 1. event Event1(string assetName, address toAdd); 2. event Event1(string indexed ...
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0answers
207 views

Can I subscribe to events emitted by another contract?

I am trying to subscribe to an event emitted by an existing library's smart contract. I've found examples of how to subscribe to events emitted by my contract using web sockets and my contract ABI as ...
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1answer
54 views

How to display the value of a variable using remix debugger and emit

pragma solidity ^0.5.1; contract test { event test_value(uint256 indexed value1); uint256 value_test; function test_f() public { //value_test processing emit test_value(...
2
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1answer
27 views

Event and method different address type

This is my contract pragma solidity ^'0.5.2'; contract MyContract { address[] public contracts; event ContractCreated(address newAddress); constructor() public { } function ...
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0answers
20 views

Can't get event data selecting the event by name

This is my contract pragma solidity ^'0.5.2'; contract MyContract { event ContractCreated(address newAddress); constructor() public { } function createOtherContract() public { ...
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1answer
319 views

myContract.getPastEvents(“allEvents”) returns empty array

I want to get all past events from a contract I deployed on the Ropsten network. Contract is: pragma solidity ^0.5.1; contract SampleContract { uint storageData; event MamboNumberTwo(uint ...
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1answer
87 views

Get past events of a contract without ABI using Web3?

I'm building a simple explorer and I would like to list events emitted by contracts. Since I can't know the ABI of each contract, is it possible to get past events from a contract using Web3? If I ...
6
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4answers
2k views

Proving the Existence of Logs to the Blockchain

To preface this: I'm not entirely sure this question makes any sense. Just a thought I had that I wanted to check the feasibility of. I'm pretty sure it is possible to use a Merkle proof to show that ...
1
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1answer
394 views

Show an event with nodejs

in my Smart Contract I have a function such that it fires an event at the end of its code. function sendTran(arguments) public { *code* emit Event(argument 1,argument 3,argument 3,...
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1answer
251 views

Infura Web Sockets doesn't work on Infura

I have a problem with connecting via Websockets to Infura. I am listening on some events from my smart contract, so when some event is dispatched by calling some method from smart contract, I should ...
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1answer
52 views

Is there an issue using event overloading and event logs that contain arrays?

My event fires, but the last parameter is never logged. It appears as if it doesn't even exist. Here is my solidity code: pragma solidity >=0.5.6; contract EventTest { event marketCreated(...
3
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1answer
40 views

How is The Graph a decentralised solution?

I understand that querying for data on Ethereum is a pain in the neck and that The Graph indexes events so that developers can more easily get their most precious blockchain data. However, I'm not ...
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1answer
13 views

where does faile event go in eth contract?

If a function has multi events , the first successed but second faile. Can I get all of them in block? solidity code like this emit event1 throw emit event2
2
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1answer
88 views

NEthereum, Number of indexes don't match the number of topics

I would like to get all Transfer events for a specific interval of blocks. When I call GetAllChanges with the following parameters, I get this error message: 'Number of indexes don't match the ...
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1answer
59 views

Emit not firing event more than once

I'm experimenting a little bit with the blockchain, I'm currently trying to send from an oracle an address to store on the blockchain through a smart contract. The code (very simple and without checks)...
2
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0answers
61 views

How can I extract sidechains (transient forks) from a geth node before they get discarded?

According to my understanding, transient forks (also known as sidechains in geth's source code) are discarded or overwritten when a reorganization happens. But before that, when the node detects a ...
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2answers
49 views

Solidity events and its's necessity

I don't understand solidity events at all. For example: https://rinkeby.etherscan.io/address/0xc5a79064168c0aa3706c33d70b94a09103e9656b#events Some events show its names, others show methods without ...
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0answers
56 views

Web3 Daemon Event listner

const DManage = new web3.eth.Contract(myABI, '0x9420D0904B2F696f8612239e5a507A86B5dA1b6a'); DManage.events.allEvents() .on('data', (response) => { console.log(event); }) .on('changed', (...
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2answers
98 views

How do I monitor 50k addresses for incoming ERC20 transactions?

I have a list of 50.000 Ethereum addresses which at any time may receive ERC20 transfers. I know I can create filters but I don't think it scales to send 50.000 RPC calls to an Ethereum node every 20 ...
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1answer
19 views

Trigger manual DB UPSERTs through smart contract

Can I add a trigger to smart contract to insert/update data to my traditional DB. E.g. Let's say I have students private blockchain where each student has to update their info. Once they insert/update ...
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0answers
35 views

How do i retrieve the transaction hash to DApp's frontend?

I have a simple DApp that stores data, developed with truffle and deployed on rinkeby, and I want to show the transaction hash in the frontend. I've read a lot about web3.eth.getTransaction() or ...
6
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4answers
1k views

Duplicate events firing in a Web3 listener

I'm experimenting with plugging Ethereum into a React web application, using this nice tutorial repo as a basis (thanks to uzyn): https://github.com/uzyn/ethereum-webpack-example-dapp I'm connecting ...
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0answers
47 views

How do newHeads and event subscriptions behave on past reorgs?

Based on the geth documentation, I understand that a subscription on both newHeads and logs will emit all new heads and events that come from a reorg. However, I couldn't find what the behaviour is ...
1
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3answers
2k views

How to see events in Remix - Solidity

I am new to solidity and trying to deploy a contract to see whether the address is EOA or Smart Contract. The code is listed below. I am not able to see the boolean value when I executed the contract ...
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0answers
32 views

Event - Filtering a BigInt (or a BigNumber)

I am trying to filter on a BigInt for an event (the number can fit in a uint256). I keep getting an error Error: invalid number value This is what the code looks like.. { filter: {fromID:BigInt(...
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0answers
186 views

using events in private blockchain raises leveldb not found error

i'm getting { [Error: Node error: {"code":-32000,"message":"leveldb: not found"}] when trying to use events on a private eth blockhain. What might be the problem? (I've installed Leveldb with brew) ...
3
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1answer
349 views

Could event watch() traverse from latest block number(tail) to head?

In general, I assume events traverse from smaller to larger block number. Example: contractDeployedBlockNumber = 10000 fromBlock: contractDeployedBlockNumber, toBlock: 'latest' [Q] Could event ...
1
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1answer
982 views

Solidity event listener

This web3js event listener is part of a Voting Dapp. The listener listens for a transactions and re-renders the page to show updates. listenForEvents: function() { App.contracts.Election.deployed()....
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0answers
50 views

Best way to support restoring of all the keys of a mapping

I have a contract, in which I maintain the keys of a mapping in two different ways: Storing each key in an array Emitting an event for each key I do this in order to be able to restore the keys (and ...
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0answers
15 views

One rpc connection faster than another

I have four synced peer nodes running on two separate machines. Nodes 1-3 have been around since the beginning of the block chain and are all on one machine while Node 4 was just added around block ...
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0answers
39 views

Private blockchain losing access to older blocks

So, my private blockchain became out of sync and one of the nodes reset to block 0 – it then synced up with the other nodes. The node that went to block 0 is the node that is providing the rpc port ...
0
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1answer
30 views

Event suddenly disapears when i call another function in my contract

So i am doing a factory for an ERC20 token contract, here is my factory code: pragma solidity >= 0.4.0 < 0.6.0; import "./ERC20.sol"; import "./ERC20Interface.sol"; contract Factory { ...
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2answers
106 views

Events loading too slow

I have a dapp running on rinkeby at the moment, you can try it now on cryptogol.io, but I am facing a problem when reading events from the Blockchain. For example, yesterday I make the events happens, ...
0
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2answers
463 views

Contract event - transactionIndex and logIndex

I need to monitor contract events and perform off-chain processing. How do I uniquely identify a contract event? Can I use a combination of these fields? - transactionHash - transactionIndex - ...
3
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2answers
647 views

What is the difference between getPastEvents() vs events.MyEvent({ fromBlock: 0})?

What is the difference between using myContract.getPastEvents() to get past events and using myContract.events.MyEvent({ fromBlock: 0, }) ? Also, if I pass to fromBlock a block number that has not ...
0
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1answer
163 views

Get the output value

I am making a transaction using the function, simple.multiply.sendTransaction(5,6{from:"0xcf03e41ee1116bed4f1acf8a2209b4d37d755988"}) This is a simple function which multiplies the two numbers 5 &...
0
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1answer
101 views

Cannot watch any event on Ropsten

I'm not able to watch and log event sent by smart contract using the Ropsten test network. The same code works on local test network. Contract Event code: event CreateOptionEvent(address indexed ...
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3answers
2k views

Find topic[0], topic[1], topic[2]

As suggest in What is topics[0] in Event logs? I am trying to find out 'Event hash' but it's not matching the output for below transaction. Input Data Function: transfer(address _to, uint256 _value)...
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0answers
40 views

drizzle not updating events properly - duplicate events

I'm facing a peculiar problem while rendering event values in a component using drizzle. When a new event is created and is updated in the events array of drizzle (drizzleState.contracts.MyContract....
32
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1answer
11k views

What are event topics?

I know that indexed arguments index the values for those arguments so that filtering will be faster. But what are topics? And what are they used for? I know that signature of an event is a topic. ...
0
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1answer
65 views

why several Draw event logs when there is actually one?

I'm looking into the event logs of makerdao's CDP operation, and I'm confused why there are several event logs for 1 cdp operation, like this tx: https://etherscan.io/tx/...
1
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1answer
218 views

Getting all ERC721 transactions by an account

My approach here was to listen for Transfer event for a contract (e.g. Cryptokitties) filtered by the indexed from account. var contract = new web3.eth.Contract(kittyABI, kittyContractAddress, {from:...
0
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1answer
168 views

Recover solidity funcion event in web3j

EthFilter filter = new EthFilter(DefaultBlockParameterName.EARLIEST, DefaultBlockParameterName.LATEST, userContract.getContractAddress().substring(2)); I am trying to recover the event response that ...
2
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1answer
168 views

Ethereum smart contract update, transactions and events

I have a question about versioning of smart contracts in Ethereum. Lots of articles have been written about how to decouple your logic and data, how to use interfaces when referencing other contracts, ...