Mastering iOS App Architecture: Principles, Layering, and Common Folder Pitfalls

What is client app architecture?

iOS client‑app architecture is as complex as server‑side architecture, but its focus differs: it emphasizes safe network API usage, smooth page display, efficient local data persistence, and mechanisms for dynamic deployment without releasing new versions.

Key concerns

Network API : enable business engineers to call APIs safely and ensure good user experience under varying network conditions.

Page display : organize UI to minimise coupling and reduce development complexity for business teams.

Local persistence : arrange data locally to meet performance and consistency requirements.

Dynamic deployment : deliver new content or urgent bug fixes without a full app release.

Team‑level considerations

Collect user data to provide product and operation insights.

Organise business modules and shared infrastructure clearly.

Automate daily builds and provide testing tools for QA engineers.

Architecture design methodology

The author proposes six steps:

Identify the problems to solve and their necessary conditions.

Classify problems into modules.

Clarify dependencies, establish communication standards, and design modules.

Predict future directions, add new modules when needed, and record baseline data.

Implement core modules first, then stack them to form the full architecture.

Run unit and performance tests, use data to optimise and demonstrate value.

The overall principle is top‑down design, bottom‑up implementation, then measure before optimise.

Layering discussion

Common layer models include three‑layer (presentation, business, data) and four‑layer (presentation, business, network, local data) schemes. The author stresses that layering should emerge after identifying modules; start with problem identification, then refine layers as needed, typically ending with three logical layers.

Common folder debate

Using a generic Common folder (or pod) encourages tangled dependencies and makes future refactoring painful. Instead, create fine‑grained modules (e.g., Location, ImageProcess) so each can evolve independently, reduce build size, and improve maintainability.

Source: infoQ – http://www.infoq.com/cn/articles/ios-app-arch-part-01#rd