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Website: Amend /docs/developers/dapp-developer/native: (#27880)

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* Amend /docs/developers/dapp-developer/native:
1. Fix type
2. Fix slice of common.Hash slice syntax.
3. Clarify how the hex string for the Transfer event is computed so the code matches with the description.

* Incorporate feedback on PR + update code for blocknum typecasting
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Zubin 2023-08-24 05:17:50 +10:00 committed by GitHub
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commit d3f9d785f8
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docs/developers/dapp-developer/native.md
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@ -86,18 +86,27 @@ nonce, err := cl.NonceAt(context.Background(), addr, big.NewInt(14000000))
### Querying past events {#querying-past-events}
Contracts emit events during execution which can be queried from the client. The parameters for the event one is interested in have to be filled out in the `ethereum.FilterQuery` object. This includes which event topics are of interested, from which contracts and during which range of blocks. The example below queries `Transfer` events of all ERC-20 tokens for the last 10 blocks:
Contracts emit events during execution which can be queried from the client. The parameters for the event one is interested in have to be filled out in the `ethereum.FilterQuery` object. This includes which event topics are of interest, from which contracts and during which range of blocks. The example below queries `Transfer` events of all ERC-20 tokens for the last 10 blocks:
```go
blockNum, err := cl.BlockNumber(context.Background())
blockNumber, err := cl.BlockNumber(context.Background())
if err != nil {
return err
fmt.Println("Failed to retrieve block number:", err)
return
}
blockNumberBig := big.NewInt(int64(blockNumber))
eventSignatureBytes := []byte("Transfer(address,address,uint256)")
eventSignaturehash := crypto.Keccak256Hash(eventSignatureBytes)
q := ethereum.FilterQuery{
FromBlock: new(big.Int).Sub(blockNum, big.NewInt(10)),
ToBlock: blockNum,
Topics: [][]common.Hash{common.HexToHash("0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef")},
FromBlock: new(big.Int).Sub(blockNumberBig, big.NewInt(10)),
ToBlock: blockNumberBig,
Topics: [][]common.Hash{
{eventSignaturehash},
},
}
logs, err := cl.FilterLogs(context.Background(), q)
if err != nil {
return err