Holochain Development Skill

Patterns for developing Holochain 0.6 hApps with HDI 0.7 integrity zomes and HDK 0.6 coordinator zomes.

Environment

This project uses Nix flakes (flake.nix ), not shell.nix :

nix develop # Enter dev shell nix develop --command bun test:unit # Run unit tests in Nix bun build:zomes # Build Rust zomes bun build:happ # Build complete hApp

Key Reference Files

• Integrity zome: dnas/requests_and_offers/zomes/integrity/service_types/src/lib.rs

• Coordinator zome: dnas/requests_and_offers/zomes/coordinator/requests/src/lib.rs

• Coordinator CRUD: dnas/requests_and_offers/zomes/coordinator/requests/src/request.rs

• Entry types: dnas/requests_and_offers/zomes/integrity/requests/src/request.rs

• Shared utils: dnas/requests_and_offers/zomes/coordinator/utils/

• Tryorama tests: tests/src/requests_and_offers/

Holochain 0.6 Key Patterns

Integrity Zome (HDI 0.7)

Uses hdi::prelude::* (NOT hdk ):

use hdi::prelude::*;

#[derive(Serialize, Deserialize)] #[serde(tag = "type")] #[hdk_entry_types] #[unit_enum(UnitEntryTypes)] pub enum EntryTypes { MyEntry(MyEntry), }

#[hdk_entry_helper] #[derive(Clone, PartialEq)] pub struct MyEntry { pub name: String, pub description: String, }

#[derive(Serialize, Deserialize)] #[hdk_link_types] pub enum LinkTypes { MyEntryUpdates, AllMyEntries, }

#[hdk_extern] pub fn validate(op: Op) -> ExternResult<ValidateCallbackResult> { match op.flattened::<EntryTypes, LinkTypes>()? { FlatOp::StoreEntry(store_entry) => match store_entry { OpEntry::CreateEntry { app_entry, .. } | OpEntry::UpdateEntry { app_entry, .. } => match app_entry { EntryTypes::MyEntry(entry) => validate_my_entry(entry), }, _ => Ok(ValidateCallbackResult::Valid), }, _ => Ok(ValidateCallbackResult::Valid), } }

Coordinator Zome (HDK 0.6)

Uses hdk::prelude::* :

use hdk::prelude::; use my_integrity::;

// Create: create_entry + get + create_link to path #[hdk_extern] pub fn create_my_entry(input: MyEntryInput) -> ExternResult<Record> { let hash = create_entry(&EntryTypes::MyEntry(input.entry))?; let record = get(hash.clone(), GetOptions::default())? .ok_or(wasm_error!(WasmErrorInner::Guest("Entry not found".into())))?; let path = Path::from("my_entries.active"); create_link(path.path_entry_hash()?, hash, LinkTypes::AllMyEntries, ())?; Ok(record) }

// Read: get with GetOptions::default() #[hdk_extern] pub fn get_my_entry(hash: ActionHash) -> ExternResult<Option<Record>> { get(hash, GetOptions::default()) }

// List: LinkQuery::new() with GetStrategy #[hdk_extern] pub fn get_all_my_entries() -> ExternResult<Vec<Record>> { let path = Path::from("my_entries.active"); let link_filter = LinkTypes::AllMyEntries.try_into_filter() .map_err(|e| wasm_error!(WasmErrorInner::Guest(e.to_string())))?; let links = get_links(LinkQuery::new(path.path_entry_hash()?, link_filter) .get_options(GetStrategy::Local))?; let get_input: Vec<GetInput> = links.into_iter() .filter_map(|link| link.target.into_action_hash()) .map(|hash| GetInput::new(hash.into(), GetOptions::default())) .collect(); let records: Vec<Record> = HDK.with(|hdk| hdk.borrow().get(get_input))? .into_iter().flatten().collect(); Ok(records) }

// Update: update_entry + create tracking link #[hdk_extern] pub fn update_my_entry(input: UpdateInput) -> ExternResult<Record> { update_entry(input.previous_hash, &input.updated_entry)?; // ... get and return updated record }

// Delete link: requires GetOptions::default() delete_link(create_link_hash, GetOptions::default())?;

Signals & Post-Commit

See coordinator-zome.template.rs for Signal enum and post_commit pattern.

Project Structure

Integrity zomes (hdi ) define types + validation; coordinator zomes (hdk ) implement business logic. DNA manifest at dnas/requests_and_offers/workdir/dna/dna.yaml uses path field (not bundled ).

Common Tasks

• Add entry type: Create struct with #[hdk_entry_helper] in integrity, add to EntryTypes enum

• Add link type: Add variant to LinkTypes enum in integrity, use in coordinator

• Add zome function: Add #[hdk_extern] function in coordinator, call from frontend service

• Path indexing: Use Path::from("entity.status") for collection queries

• Batch get: Use HDK.with(|hdk| hdk.borrow().get(get_input))? for efficient multi-get

Troubleshooting

• Build failures: Ensure nix develop shell is active

• DHT sync in tests: Add dhtSync() calls between agent operations

• Link queries: Use GetStrategy::Local for reading own data, GetStrategy::Network for others

• Permission errors: Check agent_info()?.agent_initial_pubkey matches expected author