Breaking Up with Big ViewModels

on YouTube ↗35m

" summary

Breaks a 1,376-line ViewModel into multiple, screen-scoped ViewModels backed by a shared Mediator that holds only transient UI state; a gallery example uses three ViewModels (grid, top bar, bottom bar) and shows selection updates flowing via the Mediator, not direct VM-to-VM calls. Uses Jetpack Compose, Hilt or Koin scoping for one mediator per navigation destination, tests with Kotest behavior specs, and enforces the pattern with lint-as-tests via Consist (and Harmonize for iOS). Mediator pattern 1,376-line ViewModel

AI-written summary · about

" chapters (7)

1. 0:00Introduction
2. 8:06Why ViewModels become too large
3. 13:24Mediator pattern
4. 20:28Implementing mediators
5. 25:48Testing ViewModels
6. 30:43Lint rules enforcement
7. 33:51Summary

" related talks

• 41mBreaking ViewModels into smaller self-contained UI modelsHakan Bagci · droidcon New York 2024
• 40mComposing ViewModels:Breaking ViewModels into smaller self-contained UI modelsHakan Bagci · Droidcon London 2023
• 40mComposing ViewModels: Breaking ViewModels into smaller self-contained UI modelsHakan Bagci · droidcon Berlin 2023
• 43mHelp! ViewModelmhidaka · DroidKaigi 2024
• 22mBloated ViewModels? What NextDAVID ODARI KIRIBWA · droidcon Berlin 2022
• 29mModern Android Development using MVI architectureBeatrice Kinya · Android Worldwide October 2022
• 35mBreaking Up with WebViews: Server-Driven UI with KMP + ComposeAman Donk · DroidKaigi 2025
• 30mArchitecting an app with MVP and ViewModelsStephen D'Amico · droidCon NYC 2018