NEAR Random Number (u128)

random.rs

// anywhere in your contract

fn random_u128() -> u128 {
    let random_seed = env::random_seed(); // len 32
    // using first 16 bytes (doesn't affect randomness)
    as_u128(random_seed.get(..16).unwrap())
}

fn as_u128(arr: &[u8]) -> u128 {
    ((arr[0] as u128) << 0) +
    ((arr[1] as u128) << 8) +
    ((arr[2] as u128) << 16) +
    ((arr[3] as u128) << 24) +
    ((arr[4] as u128) << 32) +
    ((arr[5] as u128) << 40) +
    ((arr[6] as u128) << 48) +
    ((arr[7] as u128) << 56) +
    ((arr[8] as u128) << 64) +
    ((arr[9] as u128) << 72) +
    ((arr[10] as u128) << 80) +
    ((arr[11] as u128) << 88) +
    ((arr[12] as u128) << 96) +
    ((arr[13] as u128) << 104) +
    ((arr[14] as u128) << 112) +
    ((arr[15] as u128) << 120)
}

Hey Matt, I am trying to use this in my contract but I get an error.
panicked at 'called Option::unwrap()on aNonevalue'
Any pointers on how to fix this?
Thanks

Are you sure it has to do with slicing the random seed value?

According to the docs it should still return a vec of u8

https://docs.rs/near-sdk/4.0.0-pre.4/near_sdk/env/fn.random_seed.html

I am not sure, but I have tried to isolate it and it seems to be the thing that fails. I am only learning rust so could totally be a simple error.

try not slicing it and logging the output, or using only 1 value from the vector.

Might be something wrong with your contract setup or the way you're running it e.g. perhaps env::random_seed isn't available in simulation tests or something?

I don't think it's available or has no real values in Rust unit tests.

Ok cool I am testing it with unit tests right now so that is probably the issue.