Swift iOS REST API Integration — Networking Layer With Codable

I will build a clean, reusable networking layer for your Swift iOS application — implementing your REST API integration using URLSession with async/await, Codable models for JSON parsing, proper error handling with typed error enums, authentication header management, request/response logging for debugging, and a mock network layer for unit testing. iOS apps that handle networking incorrectly — mixing URLSession callbacks with main-thread UI updates, swallowing errors silently, or parsing JSON with fragile manual approaches — produce crashes and data inconsistencies that are extremely difficult to debug in production.

The networking layer covers a generic HTTP client with configurable base URL and headers, endpoint enum defining all API routes and their request configuration, Codable model structs for all response types, async/await request execution with proper error propagation, authentication token injection and refresh logic, network reachability handling, response caching configuration, and a MockURLProtocol-based test double enabling offline unit testing of all network-dependent code.

This service suits iOS developers building apps that consume a REST API — social apps, e-commerce apps, SaaS mobile clients, or any app fetching remote data — who want a professional networking layer that is maintainable, testable, and handles the full complexity of real-world API integration.