Handling NEAR Types

When calling methods in a contract or receiving results from them, you will need to encode/decode parameters correctly. For this, it is important to know how the contracts encode timestamps, balances, and gas.

Searching for Smart Contract Data Types?

Check the Smart Contract Data Types section for more information on how to handle data types within smart contracts.

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Time

The block timestamp in a smart contract is encoded using nanoseconds (i.e. 19 digits: 1655373910837593990).

🌐 Javascript

Date.now() returns a timestamp in milliseconds (i.e 13 digits: 1655373910837). Make sure to convert between milliseconds and nanoseconds to properly handle time variables.

🦀 Rust

In Rust std::time::SystemTime::now() returns a SystemTime object. You can convert it to nanoseconds since UNIX_EPOCH as follows:

use std::time::{SystemTime, UNIX_EPOCH};
let start = SystemTime::now();
let since_the_epoch = start.duration_since(UNIX_EPOCH)
    .expect("Time went backwards");
let in_nanoseconds = since_the_epoch.as_nanos();
println!("Current time in nanoseconds since UNIX EPOCH: {}", in_nanoseconds);

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Deposits

Smart contracts handle NEAR amounts always using yoctoNEAR (1Ⓝ = 10^24yocto). This means that when interacting with contract's or the user's balance you will need to convert between NEAR and yoctoNEAR.

Under the hood, the network (and contracts) represent balances as u128, which are encoded as strings (since JSON cannot handle more than 52 bit integers).

Remember to always send amounts as strings (e.g. "1000000000000000000000000" for 1Ⓝ) and never as number (e.g. 1000000). Consequently, convert amounts from string whenever you want to display them to the user.

🌐 Javascript

In javascript, you can use the near-api-js library to convert between NEAR and yoctoNEAR:

import { NEAR } from '@near-js/tokens'

const units = NEAR.fromDecimal('1.5') // 1.5Ⓝ
console.log(units) // "1500000000000000000000000"

const decimal = NEAR.fromUnits('1500000000000000000000000', 2)
console.log(decimal) // 1.5

🦀 Rust

In Rust you can directly use the near_token crate to convert between NEAR and yoctoNEAR:

use near_token::NearToken

fn main() {
    const TEN_NEAR: NearToken = NearToken::from_near(10);

    assert_eq!(TEN_NEAR.to_string(), "10.00 NEAR");
    assert_eq!(TEN_NEAR.as_near(), 10);
    assert_eq!(TEN_NEAR.as_millinear(), 10000);
    assert_eq!(TEN_NEAR.as_yoctonear(), 10000000000000000000000000);

    let input_str = "0.123456 NEAR";
    let input_near: NearToken = input_str.parse().unwrap();
    assert_eq!(
        input_near,
        NearToken::from_yoctonear(123456000000000000000000)
    );

}

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Gas

When calling a contract method, you can specify how much gas you want to attach to the call. Within the network, the Gas is represented as a u64, which is encoded as a string (since JSON cannot handle more than 52 bit integers).

As a rule of thumb, functions that consume little computation can be called with 30 Tgas or less, while more complex functions may require up to 300 Tgas.

🌐 Javascript

In javascript there is no built-in library to handle gas units, but you can easily convert between them as follows:

const TGAS = 1000000000000; // 1 Tgas = 10^12 gas units

function toTgas(gas) {
    return (gas * TGAS).toString();
}

function fromTgas(tgas) {
    return (parseInt(tgas) / TGAS).toFixed(2);
}

🦀 Rust

use near_gas::NearGas;

fn main() {
    let data = "12.657 tgas";

    let near_gas: NearGas = data.parse().unwrap();

    // Convert the value to the most precise "gas" unit
    assert_eq!(near_gas.as_gas(), 12657000000000);
    // Convert the value to "gigagas" unit
    assert_eq!(near_gas.as_ggas(), 12657);
    
    // Display Gas. It will print: "Here is 12.7 Tgas"
    println!("Here is {}", near_gas);

    // When `serde` feature is enabled, NearGas can be used in serde-serializable structs.
    // NearGas will be serialized to a gas-precision u64 value encoded as string.
    #[derive(serde::Serialize)]
    struct FunctionCallDetails {
        used_gas: NearGas,
    }

    let details = FunctionCallDetails { used_gas: near_gas };

    assert_eq!(serde_json::to_string(&details).unwrap(), r#"{"used_gas":"12657000000000"}"#);
}