Zome Traits Protocol - Proposal

This is a proposal on how zome traits can be implemented.

TLDR;

Implement a macro that takes a rust trait with no &self methods and defines all its functions as hdk_extern.

This is an example on how it would look like:

• Defining a zome trait:

use zome_traits::zome_trait;

#[derive(Serialize, Deserialize, Debug)]
pub struct CreateTransactionInput {
	agent: AgentPubKey;
	amount: f64;
}

#[zome_trait]
pub trait MutualCreditZomeTrait {
	fn get_balance(agent: AgentPubKey) -> ExternResult<f64>;
	fn create_transaction(input: CreateTransactionInput) -> ExternResult<()>;
}

• Implementing a zome trait:

use zome_traits::zome_trait_extern;
use mutual_credit::MutualCreditZomeTrait;

struct HoloFuel; 

#[implement_zome_trait_as_externs]
impl MutualCreditZomeTrait for HoloFuel {

	fn get_balance(agent: AgentPubKey) -> ExternResult<f64> {
	  let links =	get_links(agent)?;

		...
	}

	fn create_transaction(input: CreateTransactionInput) -> ExternResult<()> {
	  let my_pub_key = agent_info()?.agent_latest_pubkey;
		create_entry(HoloFuelTransaction {
			sender: my_pub_key,
			recipient: input.agent,
			amount: input.amount
		})?;

		Ok(())
	}

}

implemented_zome_traits![HoloFuel] // Defines a `__zome_traits` function

Goals

• Have well defined interfaces between commonly used types of zomes.
• Enable aggregator UIs that can fetch data from different DNAs and display it in the same way.
  • Even if a DNA doesn't include a certain coordinator zome that exposes a certain zome trait, a new coordinator zome could be written for that DNA that implements a that trait, and be added to that DNA dynamically.
• Enable interoperability between DNAs.

Technical implementation

zome_trait

Macro that can be placed on a trait that enforces that there is no &self parameter in any of the methods of the trait.

implement_zome_trait_as_externs

Macro that takes the implementation of a trait and defines all its methods as #[hdk_extern].

implemented_zome_traits

Macro that takes an enum of structs and defines a __zome_traits zome function that returns the zome traits that this zome implements, and describes their function signatures with something like ts-rs.