Transferring TRC-10 in smart contracts

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Prerequisites

• TRC-10
• Writing & compiling Solidity

Since the Odyssey 3.2 release, smart contracts can transfer TRC-10 tokens directly through TRON-specific Solidity built-ins. Unlike TRC-20 — which is a contract-level standard implemented in user-deployed contracts — TRC-10 is a protocol-level token, so transferring it from inside a contract uses dedicated language extensions rather than calling another contract's transfer function.

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A TRON-specific compiler is required

The trcToken type, transferToken, msg.tokenid, and tokenBalance are TRON extensions to Solidity — they cannot be compiled by a generic Solidity compiler such as solc or Remix. Compile such contracts with the TRON solc (tron-solc) bundled with TronBox or TronIDE.

Example: TRC-10 transfer in a contract

pragma solidity 0.5.10;

contract transferTokenContract {
    constructor() payable public {}

    function() payable external {}

    function transferTokenTest(address payable toAddress, uint256 tokenValue, trcToken id) payable public {
        toAddress.transferToken(tokenValue, id);
    }

    function msgTokenValueAndTokenIdTest() public payable returns (trcToken, uint256) {
        trcToken id = msg.tokenid;
        uint256 value = msg.tokenvalue;
        return (id, value);
    }

    function getTokenBalanceTest(address accountAddress) payable public returns (uint256) {
        trcToken id = 1000001;
        return accountAddress.tokenBalance(id);
    }
}

TRON-specific TRC-10 built-ins

trcToken type

Odyssey 3.2 introduced the trcToken type, which represents a TRC-10 token ID in transfer operations.

trcToken id = 1000001;

address.transferToken(value, tokenId)

Send a TRC-10 token from a contract to an address. The recipient must be payable.

address.transferToken(uint256 tokenValue, trcToken tokenId)

address.tokenBalance(tokenId)

Query the TRC-10 token balance of an address. Returns the balance as a uint256.

address.tokenBalance(trcToken) returns (uint256 tokenAmount)

msg.tokenvalue and msg.tokenid

Within a function called with attached TRC-10 tokens, msg.tokenvalue exposes the amount and msg.tokenid exposes the token ID.

Related resources

• TRC-10 — TRC-10 standard overview
• TRC-20 — fungible token standard for new projects (recommended)
• Writing & compiling Solidity — Solidity basics on TRON