The right way to use Multiaddress

[boundless-forest]

Although paritytech/substrate#7380 has been merged for a long time, I found there are few docs that talks about how to use this feature. Some questions I have:

1. Is this feature fully developed or remaining some works to do?
2. Are there any demos or docs that show how it integrates with evm pallet?

@shawntabrizi Maybe you can help me.

[nuke-web3]

I see in the present Frontier template the Address is set:

pub type Address = sp_runtime::MultiAddress<AccountId, ()>;

and in the EVM pallet config:

type AddressMapping = HashedAddressMapping<BlakeTwo256>;

Are you looking to convert the latter to use the MultiAddress type? If so, this could look much closer to the https://docs.moonbeam.network/learn/unified-accounts/ structure for users, where the conversions/mappings could be done "under the hood" for users.

[shawntabrizi]

MultiAddress is just an encoding format.

It means that you can use the first two bytes of the encoded MultiAddress to determine which of the address types it actually is.

To use it, you basically just stick a match statement wherever you use this type.

like this:

impl<T: Config> StaticLookup for Module<T>
where
	MultiAddress<T::AccountId, T::AccountIndex>: Codec,
{
	type Source = MultiAddress<T::AccountId, T::AccountIndex>;
	type Target = T::AccountId;

	fn lookup(a: Self::Source) -> Result<Self::Target, LookupError> {
		match a {
			MultiAddress::Id(id) => Ok(id),
			MultiAddress::Address32(hash) => {
				Lookup::<T>::get(hash).ok_or(LookupError)
			},
			_ => Err(LookupError),
		}
	}

	fn unlookup(a: Self::Target) -> Self::Source {
		MultiAddress::Id(a)
	}
}

So in any pallet where you use T::AccountId as an input, you should instead use <T::Lookup as StaticLookup>::Source and then resolve the address format with T::Lookup::lookup(who)?.

Stuff like that.

[nuke-web3]

https://substrate.stackexchange.com/ could be a good place to resurface some of this for some rep 😁