TriggerConstantContract - Tron

Example code for the TriggerConstantContract gRPC method. Complete guide on how to use TriggerConstantContract gRPC method in GetBlock Web3 documentation.

This method executes a read-only smart-contract call locally, without creating a transaction. It is the primary method for reading contract state, such as a TRC-20 balance, and returns the result in constant_result.

Service

This method is served by the protocol.Wallet and protocol.WalletSolidity service.

This is a read method. It is also served by protocol.WalletSolidity, which returns only confirmed, irreversible data. Use the Solidity service for balance and payment verification.

Method

rpc TriggerConstantContract (TriggerSmartContract) returns (TransactionExtention)

Request Message

TriggerSmartContract

Field	Type	Description
owner_address	bytes	Caller address as raw bytes
contract_address	bytes	Contract address as raw bytes
data	bytes	ABI-encoded call data (selector + arguments)
call_value	int64	TRX in SUN to send with the call
fee_limit	int64	Maximum TRX in SUN to spend on Energy (write calls)

Request

grpcurl

grpcurl -H 'x-api-key: <ACCESS-TOKEN>' \
  -d '{"owner_address": "41f0cc5a2a84cd0f68ed1667070934542d673acbd8", "contract_address": "41a614f803b6fd780986a42c78ec9c7f77e6ded13c", "data": "70a08231000000000000000000000000f0cc5a2a84cd0f68ed1667070934542d673acbd8"}' \
  go.getblock.io:443 protocol.Wallet/TriggerConstantContract

Python

example.py

import grpc
# Stubs generated from java-tron's api.proto with grpcio-tools
from api import api_pb2_grpc
from core import Contract_pb2, Tron_pb2

creds = grpc.ssl_channel_credentials()
channel = grpc.secure_channel('go.getblock.io:443', creds)
metadata = [('x-api-key', '<ACCESS-TOKEN>')]
stub = api_pb2_grpc.WalletStub(channel)

response = stub.TriggerConstantContract(Contract_pb2.TriggerSmartContract(
    owner_address=bytes.fromhex('41f0cc5a2a84cd0f68ed1667070934542d673acbd8'),
    contract_address=bytes.fromhex('41a614f803b6fd780986a42c78ec9c7f77e6ded13c'),
    data=bytes.fromhex('70a08231...')), metadata=metadata)
print(response)

Go

example.go

conn, _ := grpc.Dial(
    "go.getblock.io:443",
    grpc.WithTransportCredentials(credentials.NewTLS(&tls.Config{})),
)
defer conn.Close()

client := api.NewWalletClient(conn)
ctx := metadata.AppendToOutgoingContext(
    context.Background(), "x-api-key", "<ACCESS-TOKEN>")

resp, _ := client.TriggerConstantContract(ctx, &core.TriggerSmartContract{OwnerAddress: owner, ContractAddress: contract, Data: callData})
fmt.Println(resp)

Response Message

TransactionExtention

Field	Type	Description
constant_result	repeated bytes	ABI-encoded return data of the call
energy_used	int64	Energy the call would consume as a transaction
result	Return	Execution result, with a result flag and any error

Use Cases

• Token Balances: Read a TRC-20 balance with balanceOf

• Contract State: Read view and pure functions without a transaction

• Price Feeds: Query on-chain oracle values

• Energy Estimation: Read energy_used to size a later transaction

Error Handling

Code	Status	Description
3	INVALID_ARGUMENT	A request field is missing or malformed
5	NOT_FOUND	The requested account, block, or transaction does not exist
16	UNAUTHENTICATED	The access token is missing or invalid
13	INTERNAL	The node failed to process the request