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Sebastien Lato
Sebastien Lato

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SwiftUI Plugin & Extension Architecture (Modular, Extensible Apps)

#swiftui #architecture #plugins #modular

Most apps start simple.

Then they grow:

  • new features
  • optional tools
  • enterprise add-ons
  • internal modules
  • experimental capabilities

Without structure, this leads to:

  • feature coupling
  • massive app containers
  • tangled dependencies
  • impossible refactors
  • slow builds

This post shows how to design a plugin & extension architecture in SwiftUI that:

  • keeps features modular
  • allows optional capabilities
  • scales with teams
  • supports future extensibility

This is how large apps stay maintainable.

🧠 The Core Principle

Features should be pluggable, not hardwired.

If removing a feature breaks your app, the architecture is too coupled.

🧱 1. Define a Plugin Protocol

Each feature becomes a plugin.

protocol AppPlugin {
    var id: String { get }
    func register(in container: AppContainer)
}
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Plugins:

  • declare themselves
  • register dependencies
  • expose entry points

🧬 2. Plugin Responsibilities

A plugin may provide:

  • routes
  • services
  • feature flags
  • background tasks
  • UI entry points

Example:

struct ChatPlugin: AppPlugin {
    let id = "chat"

    func register(in container: AppContainer) {
        container.register(ChatService.self)
        container.register(ChatViewModel.self)
    }
}
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The app doesn’t need to know how chat works.

📦 3. Plugin Registry

Central registry:

final class PluginRegistry {
    private(set) var plugins: [AppPlugin] = []

    func register(_ plugin: AppPlugin) {
        plugins.append(plugin)
    }
}
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At app startup:

registry.register(ChatPlugin())
registry.register(AnalyticsPlugin())
registry.register(ProfilePlugin())
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Then initialize them.

🧭 4. Dynamic Feature Availability

Plugins can be:

  • always-on
  • feature-flagged
  • role-based
  • environment-based

Example:

if flags.isEnabled(.chat) {
    registry.register(ChatPlugin())
}
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Features now become runtime capabilities.

🧠 5. Plugin-Based Navigation

Each plugin can expose routes:

protocol RoutablePlugin: AppPlugin {
    var routes: [AppRoute] { get }
}
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Example:

ChatPlugin.routes = [
    .chatList,
    .chatDetail
]
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The router builds navigation dynamically.

🔐 6. Dependency Isolation

Plugins should:

  • depend on shared domain interfaces
  • avoid direct cross-plugin imports
  • communicate via protocols

Bad:

ChatPlugin → ProfilePlugin
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Good:

ChatPlugin → UserServiceProtocol
ProfilePlugin → UserServiceProtocol
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Plugins must remain independent.

🧪 7. Testing Plugins in Isolation

Because plugins are modular:

let container = TestContainer()
ChatPlugin().register(in: container)
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You can test:

  • plugin features alone
  • plugin integrations
  • plugin failure modes

This reduces complexity.

🔁 8. Plugin Lifecycle

A plugin should support:

  • registration
  • activation
  • deactivation
  • cleanup

Example use cases:

  • enterprise modules
  • paid features
  • experimental tools
  • region-based capabilities

⚠️ 9. Common Plugin Architecture Anti-Patterns

Avoid:

  • plugins importing each other
  • plugins mutating global state
  • plugins without clear ownership
  • feature flags scattered in views
  • plugins that cannot be disabled

If you can’t remove it, it’s not a plugin.

🧠 Mental Model

Think:

App Core
 → Plugin Registry
   → Plugins
     → Services + Routes + Features
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Not:

“Everything lives in the main app target”

🚀 Final Thoughts

A plugin architecture gives you:

  • modular features
  • safer refactors
  • faster builds
  • clearer ownership
  • future extensibility

This is how:

  • design tool
  • enterprise apps
  • collaborative platforms
  • complex SaaS products

stay maintainable over time.

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