BlockHashAndNumber

Gets both the hash and number of the most recently accepted block on Starknet in a single RPC call. This method is more efficient than calling BlockNumber and BlockHash separately when you need both values.

Method Signature

func (provider *Provider) BlockHashAndNumber(
    ctx context.Context,
) (*BlockHashAndNumberOutput, error)

Source: block.go

Parameters

ctx (context.Context): Context for request cancellation and timeout

Returns

*BlockHashAndNumberOutput: Contains both the block hash and number
error: Error if the request fails

Type Definitions

BlockHashAndNumberOutput

type BlockHashAndNumberOutput struct {
    Number uint64     `json:"block_number,omitempty"`
    Hash   *felt.Felt `json:"block_hash,omitempty"`
}

BlockHashAndNumberOutput is a struct that is returned by BlockHashAndNumber.

Source: types_block.go

Usage Example

package main
 
import (
    "context"
    "fmt"
    "log"
    "os"
 
    "github.com/NethermindEth/starknet.go/rpc"
    "github.com/joho/godotenv"
)
 
func main() {
    // Load environment variables from .env file
    err := godotenv.Load()
    if err != nil {
        log.Fatal("Error loading .env file")
    }
 
    // Get RPC URL from environment variable
    rpcURL := os.Getenv("STARKNET_RPC_URL")
    if rpcURL == "" {
        log.Fatal("STARKNET_RPC_URL not found in .env file")
    }
 
    // Initialize provider
    provider, err := rpc.NewProvider(context.Background(), rpcURL)
    if err != nil {
        log.Fatal(err)
    }
 
    // Get latest block hash and number
    result, err := provider.BlockHashAndNumber(context.Background())
    if err != nil {
        log.Fatal(err)
    }
 
    fmt.Printf("Block Hash: %s\n", result.Hash)
    fmt.Printf("Block Number: %d\n", result.Number)
}

Error Handling

result, err := provider.BlockHashAndNumber(ctx)
if err != nil {
    switch {
    case errors.Is(err, rpc.ErrNoBlocks):
        log.Printf("Chain has no blocks yet")
    default:
        log.Printf("Failed to get block info: %v", err)
    }
    return
}
 
// Check if values are present
if result.Hash == nil {
    log.Printf("Block hash is nil")
    return
}
 
fmt.Printf("Block: %d, Hash: %s\n", result.Number, result.Hash.String())

Common Use Cases

Geting both hash and number in one call when you need both values. See example.
Verifying you have the correct block by checking both its number and hash. See example.
Tracking the latest block efficiently when syncing application state with the blockchain.
Confirming transactions have been included in a specific block by checking both block number and hash.