contract

Type Inference

TronWeb provides type inference for smart contracts from v6.0.4, allowing you to work with contract methods and their parameters in a type-safe manner. This feature is particularly useful when using TypeScript. To use type inference, you need to add as const assertion to the contract ABI. For example:

const abi = [
  {
    "constant": true,
    "inputs": [{ "name": "input_value", "type": "uint256" }],
    "name": "getValue",
    "outputs": [{ "name": "output_value", "type": "uint256" }],
    "payable": false,
    "stateMutability": "view",
    "type": "function"
  }
] as const;
const contract = tronWeb.contract(abi, 'contractAddress');
const value = await contract.getValue(100).call();

In the example above, you can get the parameter type of contract.getValue as Numbers and the return value type as [Numbers] & { output_value: Numbers }.

Note:

• If you want to call a contract with overloaded functions, you must use the contract[functionSelector](...args) syntax to trigger the contract, even though type inference is available when using contract[functionName](...args).
• If the ABI outputs include a field named length, the returned array will not contain this property because length is a reserved property of arrays. As a result, if length is the only output defined in the ABI, the returned value will be unwrapped and returned as a single value rather than an array.
• If a contract method argument is an array, you must either pass the array directly to the method or use as const to narrow the argument type.
• The send() method accepts a SendOptions object as its sole parameter. To ensure the correct return type is inferred, pass the object directly to the method or use as const to narrow the argument type.

Smart Contract Deployment

For deploying a smart contract, you can not only use the tronWeb.transactionBuilder.createSmartContract interface, but also the tronWeb.contract().new() interface.

Smart Contract Invocation

Get smart contract instance

Before calling a smart contract, you need to obtain the smart contract instance first. You can create a contract instance in the following way:

//Example 1
let abi = [...] as const;       
let instance = await tronWeb.contract(abi,'contractAddress'); 

Calling smart contract methods

Different types of contract methods need to be invoked by different tronweb apis:

• Use call to execute pure or view smart contract methods, please refer to method.call().
• Use send to execute non-pure or modify smart contract methods, please refer to method.send() for specific usage instructions.