iOS Networking Layer — async/await

A production-ready, reusable networking layer for iOS built with Swift async/await.
Drop it into any project and start making API calls in minutes.

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Features

• ✅ Generic — works with any Decodable response model
• ✅ async/await — modern Swift concurrency, no callbacks or Combine
• ✅ Interceptors — auto-attach auth tokens, log every request
• ✅ Retry logic — exponential backoff on timeout/connection errors
• ✅ Type-safe errors — every failure has a clear, meaningful message
• ✅ Endpoint protocol — add any new API call by adding one enum case
• ✅ Testable — every class depends on protocols, not concrete types
• ✅ Snake_case — automatic JSON key conversion (user_name → userName)

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Architecture

ViewModel
    ↓
UserService             ← calls NetworkClient, hides implementation details
    ↓
NetworkClient           ← core: builds request, runs interceptors, retries
    ↓
  ┌──────────────┐
  │ Interceptors │  → AuthInterceptor   (adds Bearer token)
  │              │  → LoggingInterceptor (prints request to console)
  └──────────────┘
    ↓
RequestBuilder          ← converts Endpoint → URLRequest
    ↓
URLSession              ← actual network call
    ↓
JSON Response
    ↓
JSONDecoder             ← decodes into your Decodable model
    ↓
ViewModel gets [User] / Post / etc.

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How to Use

1. Define an Endpoint

enum UserEndpoint: Endpoint {
    case getUsers
    case getUser(id: Int)
    case createPost(request: CreatePostRequest)

    var path: String {
        switch self {
        case .getUsers:           return "/users"
        case .getUser(let id):    return "/users/\(id)"
        case .createPost:         return "/posts"
        }
    }

    var method: HTTPMethod {
        switch self {
        case .getUsers, .getUser:   return .get
        case .createPost:           return .post
        }
    }

    var body: Encodable? {
        switch self {
        case .createPost(let req):  return req
        default:                    return nil
        }
    }
}

2. Make a Request

let client = NetworkClient()

// GET — fetch a list
let users = try await client.request([User].self, endpoint: UserEndpoint.getUsers)

// GET — fetch by ID
let user = try await client.request(User.self, endpoint: UserEndpoint.getUser(id: 1))

// POST — send a body
let post = try await client.request(Post.self, endpoint: UserEndpoint.createPost(request: req))

3. Handle Errors

do {
    let users = try await service.fetchUsers()
} catch let error as NetworkError {
    switch error {
    case .noInternetConnection:  showAlert("No internet")
    case .unauthorized:          navigateToLogin()
    case .serverError(let code): print("Server error: \(code)")
    default:                     showAlert(error.localizedDescription)
    }
}

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Project Structure

NetworkingLayer/
├── Core/
│   ├── HTTPMethod.swift          ← GET, POST, PUT, PATCH, DELETE
│   ├── NetworkError.swift        ← All error cases with descriptions
│   ├── Endpoint.swift            ← Protocol every endpoint conforms to
│   ├── RequestBuilder.swift      ← Endpoint → URLRequest conversion
│   └── NetworkClient.swift       ← Main client with retry + interceptors
├── Interceptors/
│   ├── Interceptor.swift         ← Base protocol
│   ├── AuthInterceptor.swift     ← Attaches Bearer token automatically
│   └── LoggingInterceptor.swift  ← Logs all requests in DEBUG builds
├── Endpoints/
│   └── UserEndpoint.swift        ← Real example: GET/POST/PUT/DELETE
├── Models/
│   └── User.swift                ← Decodable response models
└── Demo/
    ├── UserService.swift          ← Service layer on top of NetworkClient
    └── UsersViewModel.swift       ← ViewModel consuming the service

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Error Types

Error	When it happens
invalidURL	URL could not be constructed
noInternetConnection	Device is offline
requestTimeout	Request exceeded time limit
unauthorized	401 — token expired
forbidden	403 — no permission
notFound	404 — resource missing
serverError(statusCode)	500+ — server problem
decodingFailed	JSON didn't match the model

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Requirements

	Version
iOS	16.0+
Swift	5.9+
Xcode	15.0+

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Author

Bilal Zafar — iOS Developer
GitHub • LinkedIn