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Variable Scope System

The Nuraly micro-app architecture implements a two-tier variable scope system that provides flexible state management across different levels of isolation and sharing.

Overview​

Variables in micro-apps can exist at two different scope levels:

ScopeStorage LevelSharing BehaviorUse Cases
LOCALPer micro-app instanceIsolated - each instance has its own storageTemporary UI state, form inputs, component-specific data
GLOBALSingleton across all appsShared across ALL instances regardless of appAuthentication status, theme, language settings

Architecture Overview​

Key Points
  • LOCAL Scope: Isolated per instance, cleared on unmount, default for all variables
  • GLOBAL Scope: Shared across ALL instances, persists for session, triggers global events
  • Singleton Pattern: One SharedVariableRegistry instance for entire application

Scope Resolution Flow​

When you access a variable without an explicit scope prefix, the system automatically resolves it:

Resolution Order: LOCAL → GLOBAL → undefined

Variable Access Patterns​

Setting LOCAL Variables​

// Implicit - defaults to LOCAL
$clickCount = 5
$tempData = { foo: 'bar' }

// Explicit
$local.formData = { name: '', email: '' }

Setting GLOBAL Variables​

// Must use explicit prefix
$global.theme = 'dark'
$global.userName = 'John Doe'
$global.isAuthenticated = true

Getting Variables​

// Auto-resolution (searches LOCAL → GLOBAL)
const userName = $userName

// Explicit scope access
const theme = $global.theme  // Only checks GLOBAL
const temp = $local.tempData  // Only checks LOCAL

Complete Access Pattern Flow​

Global Variable Event Propagation​

When a GLOBAL variable changes, the event propagates to all micro-app instances:

Variable Lifecycle​

Class Structure​

Runtime Deployment​

This diagram shows how the system works in practice with real applications:

API Reference​

Publishing to Global Scope​

You can promote a LOCAL variable to GLOBAL scope:

// Start with local variable
$selectedProduct = { id: 123, name: 'Widget' }

// Publish to global scope
Runtime.publishToGlobal('selectedProduct')

// Now accessible globally
console.log($global.selectedProduct)

Subscribing to Variable Changes​

// Subscribe to variable changes
const unsubscribe = Runtime.subscribeToVar('global.theme', (newTheme) => {
  console.log('Theme changed to:', newTheme)
  updateUITheme(newTheme)
})

// Cleanup when done
unsubscribe()

Best Practices​

Guidelines
  1. Use LOCAL by default - Keep variables private unless needed elsewhere
  2. Use GLOBAL sparingly - Only for truly global state (auth, theme, etc.)
  3. Explicit prefixes - Use $global. prefix for clarity when setting globals
  4. Subscribe carefully - Always unsubscribe to prevent memory leaks
  5. Avoid large objects - GLOBAL variable changes trigger updates in ALL instances
  6. ⚠️ Not a security boundary - All micro-apps run in same JavaScript context

Performance Considerations​

  • GLOBAL variables trigger updates in ALL instances - use judiciously
  • LOCAL variables are most performant - updates don't propagate
  • Smart Caching - Proxies cached using WeakMap for automatic garbage collection
  • Efficient Events - Only affected components refresh on variable changes

Common Patterns​

Pattern 1: Component-Specific State​

// Good - Uses LOCAL scope by default
$isLoading = true
$errorMessage = null
$formData = { name: '', email: '' }

Pattern 2: Application-Wide State​

// Good - Explicit GLOBAL for shared state
$global.theme = 'dark'
$global.userName = currentUser.name
$global.isAuthenticated = true

Pattern 3: Conditional Publishing​

// Start local, publish when needed
$draftArticle = { title: '', content: '' }

// User clicks "Share with team"
Runtime.publishToGlobal('draftArticle')

Next Steps​

  • Learn about Micro-App Architecture
  • Explore Component Communication (coming soon)
  • See Handler Execution (coming soon)