Your First App

Apps in Loom are directories containing JSON DocType definitions and Rhai scripts. No Rust toolchain is needed to develop or install apps.

Scaffold an App

loom new-app todo_app

This creates:

todo_app/
├── loom_app.toml         # App metadata
├── doctypes/             # DocType definitions
├── api/                  # Whitelisted API methods
├── scripts/              # Shared Rhai scripts
├── fixtures/             # Seed data
├── hooks.toml            # App-level hooks
└── frontend/             # Optional frontend extensions

Create a DocType

Option 1: JSON file

Create todo_app/doctypes/todo/todo.json:

{
  "name": "Todo",
  "module": "Todo App",
  "naming_rule": "autoincrement",
  "fields": [
    {
      "fieldname": "title",
      "label": "Title",
      "fieldtype": "Data",
      "reqd": true,
      "in_list_view": true
    },
    {
      "fieldname": "status",
      "label": "Status",
      "fieldtype": "Select",
      "options": "Open\nIn Progress\nCompleted",
      "default": "Open",
      "in_list_view": true,
      "in_standard_filter": true
    },
    {
      "fieldname": "priority",
      "label": "Priority",
      "fieldtype": "Select",
      "options": "Low\nMedium\nHigh",
      "default": "Medium",
      "in_list_view": true
    },
    {
      "fieldname": "description",
      "label": "Description",
      "fieldtype": "Text"
    },
    {
      "fieldname": "due_date",
      "label": "Due Date",
      "fieldtype": "Date"
    }
  ],
  "permissions": [
    {
      "role": "All",
      "read": true,
      "write": true,
      "create": true,
      "delete": true
    }
  ]
}

Option 2: Desk UI

Navigate to /app/DocType/new in the browser and use the DocType Builder.

Install the App

loom --site mysite.localhost install-app todo_app

This loads the JSON, creates the database table, and registers the DocType. Navigate to /app/Todo to see your list view, or /app/Todo/new to create a record.

Add a Script

Create todo_app/doctypes/todo/todo.rhai:

fn validate(doc) {
    if doc.due_date != () && doc.due_date < today() {
        throw("Due date cannot be in the past");
    }
}

fn before_save(doc) {
    if doc.status == "Completed" && doc.completed_on == () {
        doc.completed_on = today();
    }
    doc
}

Re-install the app or restart the server to load the script.

Add an API Method

Create todo_app/api/get_open_count.rhai:

fn main(params, loom) {
    let count = loom_db_count("Todo", #{ status: "Open" });
    #{ count: count }
}

Call it:

curl -X POST http://localhost:8000/api/method/todo_app.get_open_count \
  -H "Content-Type: application/json" \
  -d '{}'