Show events in Solana Block Explorer
In this article, we’ll explore how to display events issued by ’emit!’ in the Solana block browser.
What is emit!'?
On the Solana blockchain, "emit!" is a function used to send events to the network. This allows you to define and execute custom functions that interact with other contracts or the blockchain itself. In this case we will use it to display the event block in the browser.
Determining the structure of the event
First, let's define the event structure:
#[event]
pub struct ClaimEvent {
Pub inclusion: u64,
}
This defines a simple 'ClaimEvent' structure with a single field 'engagement', which represents the number of engagements (or interactions) in the contract.
Using emit!’
Now let’s use “emit!” to send a “ClaimEvent” block to the browser:
emit!(ClaimEvent { engagement: 123 });
However, as you mentioned above, this will only work if we define an event structure for it. To fix this, we need to add a new event type and use the event macro (available in the Solana Rust SDK) to define our custom event:
use solana_sdk::event::{Event, EventRecord};
#[event]
pub struct ClaimEvent {
Pub inclusion: u64,
}
impl event ClaimEvent {
fn signature(&self) -> &[u8] {
// Return the event signature (not shown in this example)
not implemented!()
}
}
In this updated code we define a new ‘ClaimEvent’ structure and introduce an ‘Event’ attribute. The “signature()” method is called to return the event’s metadata, but for now it returns an empty byte.
View events in Block Explorer
To display events in the block browser, you need to use the “blockchain” module:
use blockchain::{block, event, blockID};
fn main() {
// Get the current block ID
let block_id = block::BlockId::new();
// Define the event input for our custom event
let event_record = EventRecord::new();
event_record.set_field("engagement", 123);
// Create a new block object
let block_data = block_data ! {
id: block_id.to_string(),
events: some(old![event_record.clone()]),
};
// Sending a block of data to the blockchain
let mut tx = block::Transaction::new().set_data(block_data).signer().build();
blockchain::send_transaction(&tx, "my transaction");
}
In this example, we use the “blockchain” module to create a new blockchain object and add our custom event record to it. We then send the block data to the blockchain using the “send_transaction()” function.
Examples of use
This example shows how to display events in the Solana block explorer. You can apply similar logic to other contracts or integrations, such as:
- View user engagement metrics
- View transaction history
- API call logging
Note that this is a simplified example and factors such as event persistence, logging, and security should be considered when implementing custom events on the Solana blockchain.