Obtaining the "to" Address for a Change Output

Sway
1

Hey all,

Below is a snip of a loop i have in Sway, going over the outputs in the tx, It simply logs the output type, asset_id, an “to” address.

The end goal of this loop (not implemented) is when i find the output type Output::Change, I want to also discover what the “to” address is and validate the change is going back to a specific address.

However when I log the results of these function calls. For the Change output I get a None in place where I would expect the change return address, and also, a None in the asset id place.

I’m assuming these fields are not populated yet in this part of the transactions execution?

      let out_count = output_count();
      log(out_count);
      let mut j = 0;
      while j < out_count {

          let o_ass_id = output_asset_id(j);
          log(o_ass_id);

          let o_ass_to = output_asset_to(j);
          log(o_ass_to);

          let o_type = output_type(j);
          log(o_type);


          j += 1;
      }

Logged output: Ok("None"), Ok("None"), Ok("Change")

Ok("None")  --> output asset id (should be the default asset id)
Ok("None")  --> output asset to address (where the output has the change to go back to)
Ok("Change")  --> Output type (Change)

Is there any way I can investigate the Change to address at this point in the execution? Or is there another technique?

edit:

from outputs.sw this explains the None for the asset id and “to”

pub fn output_asset_id(index: u64) -> Option<AssetId> {
    match output_type(index) {
        Output::Coin => Some(AssetId::from(__gtf::<b256>(index, GTF_OUTPUT_COIN_ASSET_ID))),
        _ => None,
    }
}

pub fn output_asset_to(index: u64) -> Option<b256> {
    match output_type(index) {
        Output::Coin => Some(__gtf::<b256>(index, GTF_OUTPUT_COIN_TO)),
        _ => None,
    }
}

So i guess is there any way to investivate the output change to address at all?

In metadata.rs in the fuel-vm there doesn’t look like there are any GTFArgs for “::OutputChange”

2

Hey @Antony, this functionality is missing at the moment.

You can track the status of the issue here:

I’ll reach out to our VM team and check on the status of it.

1 Like
3

Hi @david , thanks for that! :slight_smile: