---
description: >-
  Learn about 'triggerconstantcontract' in Tron's HTTP REST API  Interface for
  querying smart contracts without on-chain transactions.
---

# triggerconstantcontract - TRON

## Description

The 'triggerconstantcontract' HTTP REST API protocol method in Tron allows developers to query smart contract states without submitting transactions to the blockchain. This Web3-compatible function is part of the HTTP REST API Interface, enabling read-only operations like fetching contract data or simulating executions. Ideal for dApps, wallets, and explorers, 'triggerconstantcontract' ensures efficient, gas-free interactions with smart contracts. Use it to retrieve values, validate conditions, or debug contracts seamlessly within the Tron ecosystem. Supports ABI-encoded inputs and outputs for compatibility with Ethereum tooling.

## Supported Networks

The triggerconstantcontract HTTP REST API method supports the following network types

* **Mainnet**
* **Testnets**

## Parameters

**wner\_address**

* **Type**: `string`
* **Default**: `TSNEe5Tf4rnc9zPMNXfaTF5fZfHDDH8oyW`
* **Description**:\
  The address that triggers the contract execution.\
  If `visible=true`, the address should be provided in Base58Check format. Otherwise, it must be in hexadecimal format.\
  For constant calls, you can use an all-zero address.

***

**contract\_address**

* **Type**: `string`
* **Default**: `TG3XXyExBkPp9nzdajDZsozEu4BkaSJozs`
* **Description**:\
  The address of the smart contract to be called.\
  Similar to `owner_address`, if `visible=true`, use Base58Check format; otherwise, use hex format.

***

**function\_selector**

* **Type**: `string`
* **Default**: `balanceOf(address)`
* **Description**:\
  Specifies the function to call on the smart contract. This field must not be left blank.

***

**parameter**

* **Type**: `string`
* **Default**: `000000000000000000000000a614f803b6fd780986a42c78ec9c7f77e6ded13c`
* **Description**:\
  The parameters for the function call, encoded according to the ABI (Application Binary Interface) specification.\
  Encoding rules are complex; it is recommended to use libraries such as `ethers.js` for encoding.\
  For more details, refer to the documentation: _Guide - Smart Contract - Best Practice - Parameter Encoding and Decoding_.

***

**visible**

* **Type**: `boolean`
* **Default**: `true`
* **Description**:\
  Optional field.\
  Indicates whether addresses are in Base58Check format (`true`) or hexadecimal format (`false`).

### URL

```json
https://go.getblock.io/<ACCESS-TOKEN>/
```

Here’s a sample cURL request using triggerconstantcontract

Request

```json
curl --request POST \
     --url https://api.shasta.trongrid.io/walletsolidity/triggerconstantcontract \
     --header 'accept: application/json' \
     --header 'content-type: application/json' \
     --data '
{
  "owner_address": "TSNEe5Tf4rnc9zPMNXfaTF5fZfHDDH8oyW",
  "contract_address": "TG3XXyExBkPp9nzdajDZsozEu4BkaSJozs",
  "function_selector": "balanceOf(address)",
  "parameter": "000000000000000000000000a614f803b6fd780986a42c78ec9c7f77e6ded13c",
  "visible": true
}
'
```

Response

```json
{
  "result": {
    "result": true
  },
  "energy_used": 541,
  "constant_result": [
    "0000000000000000000000000000000000000000000000000000000198eb569b"
  ],
  "transaction": {
    "ret": [
      {}
    ],
    "visible": true,
    "txID": "1c6282b18448c3711673ea3523b4214e0dc0286cfe16c74eb0c25df6edb3b700",
    "raw_data": {
      "contract": [
        {
          "parameter": {
            "value": {
              "data": "70a08231000000000000000000000000a614f803b6fd780986a42c78ec9c7f77e6ded13c",
              "owner_address": "TSNEe5Tf4rnc9zPMNXfaTF5fZfHDDH8oyW",
              "contract_address": "TG3XXyExBkPp9nzdajDZsozEu4BkaSJozs"
            },
            "type_url": "type.googleapis.com/protocol.TriggerSmartContract"
          },
          "type": "TriggerSmartContract"
        }
      ],
      "ref_block_bytes": "f838",
      "ref_block_hash": "aacb9930ca029b87",
      "expiration": 1745424771000,
      "timestamp": 1745424771483
    },
    "raw_data_hex": "0a02f8382208aacb9930ca029b8740b8cfb19be6325a8e01081f1289010a31747970652e676f6f676c65617069732e636f6d2f70726f746f636f6c2e54726967676572536d617274436f6e747261637412540a1541b3dcf27c251da9363f1a4888257c16676cf54edf12154142a1e39aefa49290f2b3f9ed688d7cecf86cd6e0222470a08231000000000000000000000000a614f803b6fd780986a42c78ec9c7f77e6ded13c709bd3b19be632"
  }
}
```

## Body Parameters

**result**

* **Type**: `Return`
* **Description**:\
  The result of running the operation.\
  For detailed parameter definitions, refer to the `EstimateEnergy` section.

***

**energy\_used**

* **Type**: `int64`
* **Description**:\
  The estimated amount of energy consumed during the operation.

***

**constant\_result**

* **Type**: `string array`
* **Description**:\
  A list containing the results of the triggered functions.

***

**transaction**

* **Type**: `Transaction`
* **Description**:\
  Transaction information related to the operation.\
  For details, refer to the _GetTransactionByID_ section.

## Use Case

Here are some use-cases for the `triggerconstantcontract` method in Web3 programming:

1. **Reading Smart Contract State Without Gas Costs**\
   The `triggerconstantcontract` method allows developers to call read-only functions on a smart contract without executing a transaction on the blockchain. This is useful for fetching data like token balances, contract configurations, or stored values without spending gas.
2. **Simulating Contract Interactions**\
   Developers can use this method to test how a smart contract would respond to certain inputs without actually modifying the blockchain state. This helps in debugging and validating contract logic before executing real transactions.
3. **Querying Historical or Off-Chain Data**\
   Since `triggerconstantcontract` does not require a transaction, it can be used to retrieve historical data or off-chain computed values stored in a contract, such as price feeds, voting results, or DAO governance parameters.

This method is particularly valuable for dApps that need efficient, gas-free access to blockchain data.

## Code for triggerconstantcontract

```python
import requests

url = "https://api.shasta.trongrid.io/walletsolidity/triggerconstantcontract"
headers = {
    "accept": "application/json",
    "content-type": "application/json"
}
payload = {
    "owner_address": "TSNEe5Tf4rnc9zPMNXfaTF5fZfHDDH8oyW",
    "contract_address": "TG3XXyExBkPp9nzdajDZsozEu4BkaSJozs",
    "function_selector": "balanceOf(address)",
    "parameter": "000000000000000000000000a614f803b6fd780986a42c78ec9c7f77e6ded13c",
    "visible": True
}

response = requests.post(url, headers=headers, json=payload)
print(response.json())
```

## Common Errors

**Common Errors**\
When using the `triggerconstantcontract` REST Tron method, the following issues may occur:

* **Invalid contract address**: The provided contract address is malformed or does not exist. Ensure the address is correctly formatted (base58 or hex) and corresponds to a deployed contract.
* **Incorrect ABI or function signature**: The function call fails due to a mismatched ABI or incorrect parameter encoding. Verify the ABI and ensure input parameters match the expected types.
* **Insufficient TRX for energy**: While `triggerconstantcontract` doesn’t consume gas, it requires energy, which depends on account bandwidth or frozen TRX. Check the account’s energy resources or freeze TRX to increase bandwidth.
* **Execution reverted**: The contract function reverts due to a logical error (e.g., failed assertion). Review the contract’s source code or events to debug the revert reason.

The `triggerconstantcontract` method is ideal for Web3 apps as it enables gas-free read-only interactions with smart contracts, ensuring efficient querying of on-chain data without altering state. Its reliability and cost-effectiveness make it a cornerstone for decentralized applications (dApps) on Tron.

### conclusion

In conclusion, the **triggerconstantcontract** HTTP method is a powerful tool in the **Tron** ecosystem, enabling seamless interaction with smart contracts without consuming resources. By leveraging **triggerconstantcontract**, developers can efficiently query contract states and retrieve data, enhancing the scalability and usability of **Tron**-based applications. This feature underscores **Tron**'s commitment to providing robust, developer-friendly solutions for decentralized applications.
