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Call Contract Example

Parameters

  • contractAddress - string Contract address to interact with
  • functionName - string Smart contract function to interact with
  • abi - Array<AbiItem> (Optional) ABI of the contract to call
  • params - Array<string> (Optional) Params to call the smart contract function with
  • valueInWei - string (Optional) Amount of wei to send
  • gasLimit - string (Optional) Gas limit for the function call
  • chain - Object used to ensure the user is on the correct chain (follows the MetaMask specification)
    • chainId - string Base 10 string matching the chain id on Chainlist​
    • chainMetadata (Optional) - Object used to add the chain if the user does not have the chain added to their wallet
      • chainName - string
      • nativeCurrency - Object
        • name - string is the currency's name
        • symbol - string 2-6 characters long symbol for the chain
        • decimals - 18
      • rpcUrls - Array<string> is an array of rpc node urls that can be used to make requests. We recommend selecting a few from the listing on Chainlist​
      • blockExplorerUrls (Optional) - Array<string> is an array of block explorers that can be used with the chain
      • iconUrls (Optional) - Array<string> is currently unused by MetaMask

Request

This request reads the name of a contract.
curl
Unity
Unreal Engine C++
curl --location --request POST "localhost:9680/callContract" \
--header 'Content-Type: application/json' \
--data-raw '{
"contractAddress": "0xdac17f958d2ee523a2206206994597c13d831ec7",
"functionName": "totalSupply",
"params": [],
"abi": [
{
"inputs": [],
"name": "totalSupply",
"outputs": [
{
"internalType": "uint256",
"name": "",
"type": "uint256"
}
],
"stateMutability": "view",
"type": "function"
}
],
"chain": { "chainId": "1", "chainMetadata": { "chainName": "Ethereum", "nativeCurrency": { "name": "ETH", "symbol": "ETH", "decimals": 18 }, "rpcUrls": ["https://rpc.ankr.com/eth"] } }
}'
​
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Networking;
​
public class CallContract : MonoBehaviour
{
void Start()
{
StartCoroutine(Call());
}
​
private IEnumerator Call()
{
string jsonString = "{ \"contractAddress\": \"0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48\", \"functionName\": \"totalSupply\", \"params\": [], \"abi\": [ { \"inputs\": [], \"name\": \"totalSupply\", \"outputs\": [ { \"internalType\": \"uint256\", \"name\": \"\", \"type\": \"uint256\" } ], \"stateMutability\": \"view\", \"type\": \"function\" } ], \"chain\": { \"chainId\": \"1\", \"chainMetadata\": { \"chainName\": \"Ethereum\", \"nativeCurrency\": { \"name\": \"ETH\", \"symbol\": \"ETH\", \"decimals\": 18 }, \"rpcUrls\": [\"https://rpc.ankr.com/eth\"] } } }";
byte[] jsonBytes = System.Text.Encoding.UTF8.GetBytes(jsonString);
​
UnityWebRequest request = new UnityWebRequest("localhost:9680/callContract", "POST");
request.uploadHandler = new UploadHandlerRaw(jsonBytes);
request.downloadHandler = new DownloadHandlerBuffer();
request.SetRequestHeader("Content-Type", "application/json");
​
yield return request.SendWebRequest();
Debug.Log(request.error);
string totalSupply = request.downloadHandler.text;
Debug.Log(totalSupply);
}
}
​
#include "HyperPlayUtils.h"
#include "Endpoints/SendContract.h"
​
void OnResponse(FString Response, int32 StatusCode)
{
const bool bWasSuccessful = HyperPlayUtils::StatusCodeIsSuccess(StatusCode);
​
UE_LOG(LogTemp, Display, TEXT("CallContract Success: %s"), bWasSuccessful ? "true" : "false");
UE_LOG(LogTemp, Display, TEXT("CallContract Response: %s"), *Response);
}
​
int main(){
UCallContract* GetAccountsInstance = UCallContract::CallContract(nullptr,
"0xBA62BCfcAaFc6622853cca2BE6Ac7d845BC0f2Dc",
"name",
"",
{},
-1,
"",
5);
GetAccountsInstance->GetOnCompletedDelegate().AddRaw(this, &OnResponse);
GetAccountsInstance->Activate();
}

Response

The response value(s) of the smart contract method are mixed. If it returns a single value, it’s returned as is. If it has multiple return values they are returned as an object with properties and indices:
Response
Error
"FaucetToken"
Errors will have an HTTP response status 500-599
{
"message": "error description here"
}