11
votes
Accepted
Should events only be emitted in extrinsics?
Yes it is okay, and yes it definitely makes sense.
The most common example of this pattern can be found in the Balances pallet, where Balances events are emitted every time the Currency trait is ...
- 16.3k
11
votes
Accepted
Are there any event patterns for pallets to communicate within the runtime?
Events are really for the communication of state-transitions which happen on-chain to logic or services off-chain which would like to know when such a transition happens.
They're not designed to be ...
- 2,681
8
votes
How to decode ink smart contract call and event data?
Having this data in hex format, you can decode it using cargo-contract command line utility simply like this (run from the contract src folder):
cargo contract decode -d <data_hex_string> -t ...
7
votes
How to verify upward teleport on Relay Chain?
We have built this tool to find XCM events cross different chains https://parachain-utilities.vercel.app/xcm
Code: https://github.com/AcalaNetwork/parachain-utilities/blob/...
- 826
7
votes
Accepted
Which data to put in a Pallet Event?
For Substrate events are also "expensive". Events are in the state of each block. This means that archive nodes for example need to store all events of all blocks that ever happened. So, if ...
- 11.8k
6
votes
Accepted
Browse events in Polkadot.js/api
For events (or any queries) at a specific point in the chain -
// Get an API decorated at a specific point. This will -
// - connect
// - retrieve the metadata
// - decorate the API based on ...
- 5,985
6
votes
Accepted
How to parse/match a specific frame_system event?
The code removed in this PR is exactly what you need to do. Trying to translate it into your case would yield:
#[pallet::hooks]
impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet&...
- 2,864
5
votes
How to decode ink smart contract call and event data?
Typically all data is SCALE encoded for Substrate. You need to decode and parse the result into something human readable, like is done on the contracts-ui from the contracts-ui github and documented ...
- 1,852
5
votes
Accepted
Correlate events with extrinsics in a utility.batch call in Polkadot
The utility.batch call emits events which allow you to organize which extrinsic events are coming from each extrinsic.
Between each call, you should see an Event::ItemCompleted after an extrinsic as ...
- 16.3k
5
votes
Accepted
Event type & Call type
Indeed, this is where Macro magic is happening. These Event and Call types are coming from construct_runtime!, and is generating an "outer enum" which collects all the events and calls from ...
- 16.3k
4
votes
Filter events for specific account in Polkadot.js/api
The events are stored on chain as a Vec<EventRecord> - this means that when you make a query (either for latest or for a specific blockHash), that you would get set for that specific block. The ...
- 5,985
4
votes
Accepted
Events in Polkadot.js/api
The api.event.<pallet>.<event>.is(Event) is not used to create an event, rather it is used to check if an emitted event is of a specific type, returning true if this is the case. ...
- 5,985
4
votes
Accepted
Decoding events with Rust
There's two ways of decoding events in rust: statically typed and dynamically typed.
Statically you can use subxt to decode events from this SCALE encoding - it's done here for example. Basically ...
- 3,901
4
votes
How to verify upward teleport on Relay Chain?
This is currently fiddlier than it needs to be. There will be a Balances.Deposit event citing the credited account (along with the normal XCM stuff, like Xcm.UpwardMessageProcessed), but for now you ...
- 401
4
votes
error[E0599]: no function or associated item named `events` found for struct `frame_system::Pallet` in the current scope
We have specifically removed access to the Events storage item in frame_system because it could cause the user to read a huge amount of storage, and the events storage is only meant to be read offline....
- 16.3k
4
votes
Are there any event patterns for pallets to communicate within the runtime?
There are ways for pallets to communicate in the runtime, although I wouldn't use events for this (events are stored in an overlay that gets applied to storage at the end of the block (in ...
- 2,975
4
votes
Accepted
Problem running assert_last_event in tests.rs
I believe the problem here is small and easy to miss.
Substrate chains do not emit events when the block number is 0. This is to avoid hundreds or even thousands of events being generated in the ...
- 16.3k
4
votes
How to parse/match a specific frame_system event?
@kianenigma, thanks for you extended and detailed answer. There was just one small missing piece. I had to setup the TryInto<Event<Self>> to the #[pallet::config] macro or otherwise your ...
- 692
4
votes
Accepted
Emiting events does not work with cross contract calling
It is known issue, should be fixed with refactored events.
- 1,352
4
votes
How to save decoded events using polkadot.js?
All you want to do is have the data available outside the callback. So just set it to some variable -
let decoded = null
function setDecoded (value) {
decoded = value
}
contract.tx
.method({ ...
- 584
4
votes
Large event payloads unsafe?
Substrate will, by default, store every event in a block in a storage value Event of type Vec in the system module, which involves reading & writing this full vector each time, as explained here ...
- 11.8k
4
votes
How to query events?
You can do frame_system::Pallet::<T>::events() to fetch all the events emitted. Example
If you are working with mock runtime then you can directly use System::events() (System being the ...
- 85
4
votes
Event encoding in substrate pallet
Yes, event name is superficial. What actually matters is how the pallet event is encoded into bytes.
Pallet events are encoded such that the first byte represents the pallet index, and the second byte ...
- 16.3k
3
votes
What's the Substrate's equivalent of receipts in Ethereum?
Practically speaking, events are what you are looking for. It is up to the pallet implementation to define and emit these in a way that is useful for end consumers, like for use case.
If there is ...
- 1,852
3
votes
Should events only be emitted in extrinsics?
There are also examples for events that are not tied to extrinsics, or rather those submitted much earlier.
For instance the scheduler can perform an upgrade for a runtime approved via democracy. In ...
- 321
3
votes
How to build prefixed key for rocksdb
If you want to pull a specific storage item from rocksdb, it requires traversing the patricia trie in order to find the key that you want. This can become complicated quickly, and is generally a slow ...
- 373
3
votes
Accepted
How can I access custom pallet Event data in a test?
Here is a working example of a test using the pallet-template from the substrate-node-template:
#[test]
fn stackexchange_question() {
new_test_ext().execute_with(|| {
// To emit events, we ...
- 16.3k
3
votes
How can a recoverable account get notified when someone is initiated a recovery for it?
If you want to notify the user exactly when a recovery process for their account has started, there will be a Pallet Event RecoveryInitiated when the recovery process has started, which can be ...
- 16.3k
3
votes
Why are events stored?
The idea behind writing the events into the storage is to ensure they influence the state root in the block and ensure that events are stored somewhere for retrieval.
The fact that the events are ...
- 2,194
3
votes
How to save decoded events using polkadot.js?
This is a good question.
From all the examples that I have seen, it looks like you may have to have your program logic inside the signAndSend.
Also, a note that contract.tx.method({ ...
- 8,455
Only top scored, non community-wiki answers of a minimum length are eligible