How do I filter on events from contracts?

[wahlforss]

I've been trying for hours to listen to events from contracts. There is nothing in the docs on how it is done. Please tell me how.

ethjs-filter

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• Bug (https://github.com/ethjs/ethjs-filter/blob/master/.github/CONTRIBUTING.md#bug-reports)
• Feature (https://github.com/ethjs/ethjs-filter/blob/master/.github/CONTRIBUTING.md#feature-requests)

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[wahlforss]

Also, what options do I have for the filters? How do options work? Could the examples be a bit more fleshed out?

I love ETHJS other than that.

[SilentCicero]

@wahlforss thanks! Okay, so contract filtering is fairly straight forward and you can use it and learn more about it by using/viewing ethjs-contract.

Module:
https://github.com/ethjs/ethjs-contract

API Example:

const filter = simpleStore.SetComplete()
.new({ toBlock: 'latest' }, (error, result) => {
  // result null <BigNumber ...> filterId
});
filter.watch((err, result) => {
  // result null FilterResult {...}
});
filter.uninstall()
.then(result) => {
  // result Boolean
});

The contract object uses ethjs-filter inside it.

The filter code is available here, you can see we produce the solidity event SHA3 signature, that filter for it.

https://github.com/ethjs/ethjs-contract/blob/master/src/index.js#L90-L99

Lastly, ethjs-filter does not work with stateless API's like the infura endpoint. But will work with extensions like metamask that polyfill the stateful API with a stateless version.

We will soon address this by providing stateless API filtering, that does not require the node/endpoint to keep track of events.

Thanks for use ETHJS!

[wahlforss]

How do I listen to the event “NewBet” on my end? Alfred Wahlforss alfred@wahlforss.com +46 70 587 21 61

…

On 11 Dec 2017, at 18:58, Nick Dodson ***@***.***> wrote: @wahlforss <https://github.com/wahlforss> thanks! Okay, so contract filtering is fairly straight forward and you can use it and learn more about it by using/viewing ethjs-contract. Module: https://github.com/ethjs/ethjs-contract <https://github.com/ethjs/ethjs-contract> API Example: const filter = simpleStore.SetComplete() .new({ toBlock: 'latest' }, (error, result) => { // result null <BigNumber ...> filterId }); filter.watch((err, result) => { // result null FilterResult {...} }); filter.uninstall() .then(result) => { // result Boolean }); The contract object uses ethjs-filter inside it. The filter code is available here, you can see we produce the solidity event SHA3 signature, that filter for it. https://github.com/ethjs/ethjs-contract/blob/master/src/index.js#L90-L99 <https://github.com/ethjs/ethjs-contract/blob/master/src/index.js#L90-L99> Lastly, ethjs-filter does not work with stateless API's like the infura endpoint. But will work with extensions like metamask that polyfill the stateful API with a stateless version. We will soon address this by providing stateless API filtering, that does not require the node/endpoint to keep track of events. Thanks for use ETHJS! — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#4 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAEeWZ4qzfuIeTagTL00wRLVO5IjgZtfks5s_W1hgaJpZM4Q9s6H>.

[SilentCicero]

See the example above (similar to web3).

1. Setup Eth instance
2. Setup your contract object
3. Listen for your event

Example here using ethjs-query + ethjs-contract:

https://github.com/ethjs/ethjs-contract#usage

and an example here using ethjs interface module:

https://github.com/ethjs/ethjs#usage

So it would be something like:

yourContract.NewBet()
.new({ toBlock: 'latest' }, (error, result) => {
  // result null <BigNumber ...> filterId
});
filter.watch((err, result) => {
  // result null FilterResult {...}
});
filter.uninstall()
.then(result) => {
  // result Boolean
});

More examples here in the ethjs user-guide.

https://github.com/ethjs/ethjs/blob/master/docs/user-guide.md#contract-instance

[lgaroche]

Hello,
I can't make this example work either.
When I call myContract.Event().new() I get a Promise that resolves to the filter id.
On the promise object, there is no function watch: TypeError: filter.watch is not a function

On the other hand, I can do
let filter = myContract.Event().watch((err, res) => { console.log(res) })
But the events are not captured, and filter.filterId is null.
Any idea?

[SilentCicero]

Let me look into this stat. I'll get back to you later today. Thanks!

…

Sent from my iPhone

On Dec 18, 2017, at 8:03 AM, Louis ***@***.***> wrote: Hello, I can't make this example work either. When I call myContract.Event().new() I get a Promise that resolves to the filter id. On the promise object, there is no function watch: TypeError: filter.watch is not a function On the other hand, I can do let filter = myContract.Event().watch((err, res) => { console.log(res) }) But the events are not captured, and filter.filterId is null. Any idea? — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

[SilentCicero]

So it should be that you setup the event then watch. So: const someEvent = contract.Event(); someEvent.new() someEvent.watch() Try this format and let me know how it goes.

…

Sent from my iPhone

On Dec 18, 2017, at 8:03 AM, Louis ***@***.***> wrote: Hello, I can't make this example work either. When I call myContract.Event().new() I get a Promise that resolves to the filter id. On the promise object, there is no function watch: TypeError: filter.watch is not a function On the other hand, I can do let filter = myContract.Event().watch((err, res) => { console.log(res) }) But the events are not captured, and filter.filterId is null. Any idea? — You are receiving this because you commented. Reply to this email directly, view it on GitHub, or mute the thread.

[SilentCicero]

@lgaroche @wahlforss did you manage to get things working here?

[wahlforss]

Havent tried yet. Will do that soon.

…

On 20 Dec 2017, at 20:17, Nick Dodson ***@***.***> wrote: .

[arispen]

Hey @SilentCicero Same issue here. "filter.watch is not a function" It also says uknown field 'to'. Hope that helps:

Error: [ethjs-rpc] rpc error with payload {"id":6297886148885,"jsonrpc":"2.0","params":[{"to":"0x2CC25bDaBD264aB306d47938F3c701A6dF0e883A","topics":["0x92ebdf1fe2f64daffddb436aae297d78fe97201925117af65ae23ee5e5e5d36d"],"fromBlock":"0x0","toBlock":"latest"}],"method":"eth_newFilter"} {"message":"[ethjs-rpc] rpc error with payload {\"id\":7500219143375,\"jsonrpc\":\"2.0\",\"params\":[{\"to\":\"0x2cc25bdabd264ab306d47938f3c701a6df0e883a\",\"fromBlock\":\"0x0\",\"toBlock\":\"0x53923c\",\"topics\":[\"0x92ebdf1fe2f64daffddb436aae297d78fe97201925117af65ae23ee5e5e5d36d\"]}],\"method\":\"eth_getLogs\"} Error: Invalid params: unknown field 'to', expected one of 'fromBlock', 'toBlock', 'address', 'topics', 'limit'.","code":-32603}

[gasolin]

@SilentCicero the above mentioned format works

const filter = contract.SomeEvent();
filter.new()
filter.watch((err, result) => {
  if(result[0]) {
    // do something
  }
});

Though I saw 2 things unidentical:

1. it's the callback, not a promise
2. the event watch keeping update every seconds with empty result, need extra filter(as above) for it.

[SilentCicero]

That could be easily fixed, would you like to make a pr to address it?

…

Sent from my iPhone

On Apr 17, 2018, at 11:35 PM, gasolin ***@***.***> wrote: @SilentCicero the above mentioned format works const someEvent = contract.Event(); someEvent.new() someEvent.watch((err, result) => { if(result[0]) { // do something } }); Though I saw 2 things unidentical: it's the callback, not a promise the event watch keeping update every seconds with empty result, need extra filter(as above) for it. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub, or mute the thread.

[gasolin]

@SilentCicero I found the event watch keeping update every seconds issue might be related to
https://github.com/ethjs/ethjs-filter/blob/master/src/index.js#L48

Moving watcher.callback into (Array.isArray(decodedChangeResults) && changeResult.length > 0) might fix that issue (haven't test that)

[soundyogi]

Error: Invalid params: unknown field 'to', expected one of 'fromBlock', 'toBlock', 'address', 'topics', 'limit'.","code":-32603}

i get this error too :< did the api change? seem like 'to' should be 'address'

I made the RPC error go away like this but it seems I cant watch for events (watch callback is never called)

  componentDidMount(){
    console.log('mount')
    this.freed = getAPI().freedEvent()
    
    if(!this.props.address) throw new Error('no address')
    
    this.freed
      .new({ toBlock: 'latest', address: this.props.address, to: undefined })
      .then((result) => {
        console.log(result)
      })
      .catch((error) => {
        throw new Error(error)
      });

    this.freed.watch((err, result) => {
      console.log("WATCH!");
      if(err) throw new Error()
    });

  }
  onComponentWillUnmount() {
    this.freed.uninstall();
  }