Using Routers with Alamofire Network Calls

class: center, middle

# Using Routers with Alamofire Network Calls
## Christina Moulton, Teak Mobile Inc.
### [https://grokswift.com/router/](https://grokswift.com/router/)
### [https://grokswift.com/how-alamofire-router/](https://grokswift.com/how-alamofire-router/)
### [https://github.com/cmoulton/grokAlamofireRouter/](https://github.com/cmoulton/grokAlamofireRouter)

---

# Agenda

### Why Alamofire?

### Making Network Calls

### Implementing a Router

### How does it work?

### Alternate (Protocol-Oriented) Implementation

---

# Alamofire 101

## What?

- HTTP Networking library in Swift

- URLSession wrapper

## Why?

- Avoid writing same boilerplate over & over (e.g., JSONSerialization, auth, ...)

- Existing features easily used, e.g., Adapter & Retrier

- cURL command debugging :)

---

# How? URLSession GET Call
<pre><remark-code>// set up the session
let session = URLSession.shared

// set up the request
let todoEndpoint = "https://jsonplaceholder.typicode.com/todos/1"

guard let url = URL(string: todoEndpoint) else {
  print("Error: cannot create URL")
  return
}

let urlRequest = URLRequest(url: url)

// make the request
let task = session.dataTask(with: urlRequest) {
  (data, response, error) in
  // convert data to JSON
  // do stuff with response as JSON
}
task.resume()
</remark-code></pre>

---

# Alamofire Call

<pre><remark-code>let todoEndpoint = "https://jsonplaceholder.typicode.com/todos/1"

Alamofire.request(todoEndpoint)
  .responseJSON { response in
    // do stuff with response as JSON
  }
  .responseString { response in
    // do stuff with response as String
  }
  .response { response in
    // do stuff with response as Data
  }
  .responsePropertyList { response in
    // do stuff with response as plist
  }
</remark-code></pre>

---

# POST with optional arguments:
<pre><remark-code>let todosEndpoint = "https://jsonplaceholder.typicode.com/todos"
let newTodo: [String: Any] =
  ["title": "My First Todo", "completed": false, "userId": 1]
Alamofire.request(todosEndpoint,
  method: .post,
  parameters: newTodo,
  encoding: JSONEncoding.default,
  headers: nil)
  .responseJSON { ... }
</remark-code></pre>

---

# With URLRequest:

<pre><remark-code>let todoEndpoint = "https://jsonplaceholder.typicode.com/todos/1"
guard let url = URL(string: todoEndpoint) else {
  print("Error: cannot create URL")
  return
}
let urlRequest = URLRequest(url: url)

Alamofire.request(urlRequest)
  .responseJSON { response in
    // do stuff with response as JSON
  }
</remark-code></pre>

---

# cURL Statement Debugging

<pre><remark-code>let alamofireRequest = Alamofire.request(...)
  .responseJSON { response in
    // do stuff with response as JSON
  }
debugPrint(alamofireRequest)
</remark-code></pre>

Prints out:
<pre><remark-code>curl -i \
	-H "Accept-Language: en;q=1.0" \
	-H "User-Agent: grokRouterUpdate/1.0 \
	  (com.teakmobile.grokRouterUpdate; build:1; iOS 10.3.0) \
	  Alamofire/4.4.0" \
	-H "Accept-Encoding: gzip;q=1.0, compress;q=0.5" \
	"https://jsonplaceholder.typicode.com/todos/1"
</remark-code></pre>
---

# Alamofire GET Call with Router

<pre><remark-code>Alamofire.request(TodoRouter.get(1))
  .responseJSON { response in
    // do stuff with response as JSON
  }
</remark-code></pre>

## Why?

1. Abstraction: Networking details separate from making request & handling response: Network call vs. API call

2. Single location for:
- Strings for URLs
- Authentication
- Headers (could also set for session)

---

# How to Implement Router?

<pre><remark-code>import Foundation
import Alamofire

enum TodoRouter: URLRequestConvertible {
  static let baseURLString =
    "https://jsonplaceholder.typicode.com/"

case get(Int)
  case create([String: Any])
  case delete(Int)

func asURLRequest() throws -> URLRequest {
    // TODO: implement
  }
}
</remark-code></pre>

---

# URLConvertible?

<pre><remark-code>/// Types adopting the `URLRequestConvertible` protocol can be
/// used to construct URL requests.
public protocol URLRequestConvertible {
  /// Returns a URL request or throws if an `Error` was
  /// encountered.
  ///
  /// - throws: An `Error` if the underlying `URLRequest`
  /// is `nil`.
  ///
  /// - returns: A URL request.
  func asURLRequest() throws -> URLRequest
}
</remark-code></pre>

---

# HTTP Method

<pre><remark-code>func asURLRequest() throws -> URLRequest {
  let method: HTTPMethod = {
    switch self {
	  case .get:
        return .get
      case .create:
        return .post
      case .delete:
        return .delete
    }
  }()

// ...
}
</remark-code></pre>

---

# Parameters

<pre><remark-code>func asURLRequest() throws -> URLRequest {
  let method: HTTPMethod = {
    // ...
  }()

let params: ([String: Any]?) = {
    switch self {
      case .get, .delete:
        return nil
      case .create(let newTodo):
        return newTodo
    }
  }()
}
</remark-code></pre>

---

# URL

<pre><remark-code>func asURLRequest() throws -> URLRequest {
  // ...
  let url: URL = {
    // build up and return the URL for each endpoint
    let relativePath: String?
    switch self {
      case .get(let number), .delete(let number):
        relativePath = "todos/\(number)"
      case .create:
        relativePath = "todos"
    }

var url = URL(string: TodoRouter.baseURLString)!
    if let relativePath = relativePath {
      url = url.appendingPathComponent(relativePath)
    }
    return url
  }()
}
</remark-code></pre>

---

# URLRequest

<pre><remark-code>func asURLRequest() throws -> URLRequest {
  let method: HTTPMethod = { ... }()
  let params: ([String: Any]?) = { ... }()
  let url: URL = { ... }()

var urlRequest = URLRequest(url: url)
  urlRequest.httpMethod = method.rawValue

let encoding = JSONEncoding.default
  return try encoding.encode(urlRequest, with: params)
}
</remark-code></pre>

---

# Authentication

<pre><remark-code>func asURLRequest() throws -> URLRequest {
  // ...

var urlRequest = URLRequest(url: url)
  urlRequest.httpMethod = method.rawValue

// modify urlRequest as needed here
  if let token = APIManager.authToken {
    urlRequest.setValue("\(token)",
      forHTTPHeaderField: "Authorization")
  }

let encoding = JSONEncoding.default
  return try encoding.encode(urlRequest, with: params)
}
</remark-code></pre>

---

# How Does It Work?

### Create a URLRequestConvertible router enum case
### Alamofire.request(...) takes it and gets the URL request from it using asURLRequest()
### Alamofire uses that URLRequest to make the network call
### Any attached response handlers get called when the network call gets results (or times out or whatever)

### _(Plus RequestAdapter & RequestRetrier)_

---

# Alternative Implementation: Structs

<pre><remark-code>struct GetTodoURLRequestProvider: URLRequestConvertible {
  let idNumber: Int

func asURLRequest() throws -> URLRequest {
    let urlString =
      "https://jsonplaceholder.typicode.com/todos/\(idNumber)"
    return URLRequest(url: URL(string: urlString)!)
  }
}</remark-code></pre>

Use:

<pre><remark-code>let urlRequestProvider = GetPostURLRequestProvider(idNumber: 2)
Alamofire.request(urlRequestProvider)
  .responseJSON { ... }
</remark-code></pre>

---

# Route Protocol

<pre><remark-code>protocol Route {
  // ...
}

struct GetTodo: Route {
  // ...
}

struct Router: URLRequestConvertible {
  let route: Route
  func asURLRequest() throws -> URLRequest {
    let method: HTTPMethod = route.method()
    let params: ([String: Any]?) = route.params()
    let url: URL = route.url()

var urlRequest = URLRequest(url: url)
    urlRequest.httpMethod = method.rawValue

let encoding = route.encoding()
    return try encoding.encode(urlRequest, with: params)
  }
}
</remark-code></pre>

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class: center, middle