AuthPlugin.md

Creating an Authorization Plugin

It is relatively common for API requests to be authorized via a JWT (JSON Web Token) or another type of access token. In this example we will create a plugin that can be used to add a jwt to requests. First let's look at a simple example of how we might add a jwt to a request via a plugin:

struct AuthPlugin: PluginType {
  let token: String

  func prepare(_ request: URLRequest, target: TargetType) -> URLRequest {
    var request = request
    request.addValue("Bearer " + token, forHTTPHeaderField: "Authorization")
    return request
  }
}

let provider = MoyaProvider<Target>(plugins: [AuthPlugin(token: "eyeAm.AJsoN.weBTOKen")])

Now let's look at a more complex example where we might not have access to the jwt when we create the plugin and not all requests need to be signed. We can accomplish this by extending the TargetType protocol to provide information on whether or not authorization is needed and also taking a closure for providing a token.

class TokenSource {
  var token: String?
  init() { }
}

protocol AuthorizedTargetType: TargetType {
  var needsAuth: Bool { get }
}

struct AuthPlugin: PluginType {
  let tokenClosure: () -> String?

  func prepare(_ request: URLRequest, target: TargetType) -> URLRequest {
    guard
      let token = tokenClosure(),
      let target = target as? AuthorizedTargetType,
      target.needsAuth
    else {
      return request
    }

    var request = request
    request.addValue("Bearer " + token, forHTTPHeaderField: "Authorization")
    return request
  }
}

let source = TokenSource()
let provider = MoyaProvider<Target>(
  plugins: [
    AuthPlugin(tokenClosure: { return source.token })
  ]
)

source.token = "eyeAm.AJsoN.weBTOKen"