Holochain Development

Installation

Via Nix (Recommended)

# flake.nix
{
  inputs.holochain.url = "github:holochain/holochain";

  devShells.default = pkgs.mkShell {
    packages = [
      holochain
      lair-keystore
      hc  # Holochain CLI
    ];
  };
}

Via Cargo

cargo install holochain
cargo install lair_keystore

Quick Start

Create a New hApp

# Scaffold new project
hc scaffold web-app my-happ

# Structure created:
# my-happ/
# ├── dnas/
# │   └── my_dna/
# │       ├── workdir/
# │       └── zomes/
# │           └── coordinator/
# │               └── src/lib.rs
# ├── ui/
# └── workdir/

# Build the hApp
hc dna pack dnas/my_dna/workdir
hc app pack workdir

Zome Development

// zomes/coordinator/src/lib.rs
use hdk::prelude::*;

#[hdk_entry_helper]
pub struct Post {
    pub title: String,
    pub content: String,
}

#[hdk_extern]
pub fn create_post(post: Post) -> ExternResult<ActionHash> {
    create_entry(&EntryTypes::Post(post.clone()))
}

#[hdk_extern]
pub fn get_post(action_hash: ActionHash) -> ExternResult<Option<Record>> {
    get(action_hash, GetOptions::default())
}

#[hdk_extern]
pub fn get_all_posts() -> ExternResult<Vec<Record>> {
    let path = Path::from("all_posts");
    let links = get_links(path.path_entry_hash()?, LinkTypes::AllPosts, None)?;

    let posts: Vec<Record> = links
        .into_iter()
        .filter_map(|link| get(link.target, GetOptions::default()).ok().flatten())
        .collect();

    Ok(posts)
}

Entry Definitions

#[hdk_entry_defs]
#[unit_enum(UnitEntryTypes)]
pub enum EntryTypes {
    Post(Post),
    Comment(Comment),
}

#[hdk_link_types]
pub enum LinkTypes {
    AllPosts,
    PostToComments,
}

Conductor Configuration

# conductor-config.yaml
environment_path: /tmp/holochain