Struct ContractClient 

pub struct ContractClient { /* private fields */ }

Contract client for interacting with deployed contracts

Implementations

impl ContractClient

pub fn new( client: OnlineClient<PolkadotConfig>, address: ContractAddress, ) -> Self

Create a new contract client for an existing contract

pub fn with_metadata( client: OnlineClient<PolkadotConfig>, address: ContractAddress, metadata: ContractMetadata, ) -> Self

Create a contract client with metadata

pub async fn deploy( client: OnlineClient<PolkadotConfig>, wasm_code: Vec<u8>, metadata: ContractMetadata, constructor_name: &str, constructor_args: &[u8], wallet: &Wallet, salt: Option<Vec<u8>>, ) -> Result<Self>

Deploy a new contract

Arguments

• client - Subxt client
• wasm_code - Compiled Wasm code
• metadata - Contract metadata
• constructor_name - Name of the constructor to call
• constructor_args - SCALE-encoded constructor arguments
• wallet - Wallet to sign the deployment transaction
• salt - Salt for deterministic address generation

Returns

Contract client for the deployed contract

pub async fn call( &self, method_name: &str, args: &[u8], wallet: &Wallet, ) -> Result<String>

Call a contract method (mutable)

Arguments

• method_name - Name of the method to call
• args - SCALE-encoded method arguments
• wallet - Wallet to sign the transaction

Returns

Transaction hash of the call

pub async fn read( &self, method_name: &str, args: &[u8], caller: &[u8; 32], ) -> Result<Vec<u8>>

Read contract state (dry-run, doesn’t modify state)

This method performs a read-only call to a smart contract method without submitting a transaction. It uses the ContractsApi_call runtime API to execute the contract call and return the result.

Arguments

• method_name - Name of the method to call (from contract metadata)
• args - SCALE-encoded method arguments
• caller - Address of the caller (32-byte account ID, for access control checks)

Returns

SCALE-encoded return value from the contract method

Example

// Read the balance of an account from a token contract
let caller = [0u8; 32]; // Ilara's account
let result = contract.read("get_balance", &encoded_args, &caller).await?;
let balance: u128 = Decode::decode(&mut &result[..])?;

Implementation Details

This method:

1. Looks up the method selector from contract metadata
2. Encodes the call data (selector + arguments)
3. Calls ContractsApi_call runtime API via state_call
4. Decodes the ContractExecResult to extract the return data

The runtime API call is made at the latest finalized block to ensure consistent results.

pub fn address(&self) -> &ContractAddress

Get the contract address

pub fn metadata(&self) -> Option<&ContractMetadata>

Get the contract metadata