alamofire在SessionManager中更新JWT标头

Question

I have the following source code. I have an AlamoFire SessionManager and a ViewController that uses that SessionManager to make a HTTP request.

var Almgr : Alamofire.SessionManager = {
    // Create the server trust policies
    let serverTrustPolicies: [String: ServerTrustPolicy] = [
        "localhost": .disableEvaluation
    ]
    // Create custom manager
    let configuration = URLSessionConfiguration.default

    UserDefaults.standard.synchronize()
    var jwt = UserDefaults.standard.string(forKey: conf.JWT_KEY)

    var headers : HTTPHeaders = Alamofire.SessionManager.defaultHTTPHeaders

    let extraHeaders : HTTPHeaders = [
        "Authorization": "Bearer "+(jwt ?? ""),
        "Accept": "application/json"
    ]

    extraHeaders.forEach({ (k, v) in
        headers[k] = v
    })

    configuration.httpAdditionalHeaders = headers
    let man = Alamofire.SessionManager(
        configuration: configuration,
        serverTrustPolicyManager: ServerTrustPolicyManager(policies: serverTrustPolicies)
    )
    return man
}()

From the above code, you can see that, I am reading UserDefaults.standard.string for getting the value of the JWT token and send it in every HTTP request that I make.

The way I consume this Almgr is straight-forward, like, from a viewcontroller,

Almgr.request("my-url", method: .get).validate().responseJSON { response in

The problem however is, the Almgr seem to be initialised only once and even if I change the JWT token by setting it to a different value, via, UserDefaults.standard.set(jwt, forKey: conf.JWT_KEY) in the UserDefaults, its value is not fetched.

In a view controller, I have the following code:

print("Getting JWT in MyViewController", UserDefaults.standard.string(forKey: conf.JWT_KEY))
Almgr.request("my-url", method: .get).validate().responseJSON { response in

The print statement prints a different (correct) value for the JWT token than the Almgr which uses the old JWT that was there when the application was launched.

Now my question is, how can I make the Almgr always lazily evaluate the correct JWT value, always, when it is called.

I am using Alamofire 4.5 and Swift 4.0 if matters.

Answer 1

The solution is to use Request Adapters.

Relevant source code:

class AccessTokenAdapter: RequestAdapter {
    private let accessToken: String

    init(accessToken: String) {
        self.accessToken = accessToken
    }

    func adapt(_ urlRequest: URLRequest) throws -> URLRequest {
        var urlRequest = urlRequest

        if let urlString = urlRequest.url?.absoluteString, urlString.hasPrefix("https://httpbin.org") {
            urlRequest.setValue("Bearer " + accessToken, forHTTPHeaderField: "Authorization")
        }

        return urlRequest
    }
}


let sessionManager = SessionManager()
sessionManager.adapter = AccessTokenAdapter(accessToken: "1234")

sessionManager.request("https://httpbin.org/get")

Documentation link: https://github.com/Alamofire/Alamofire/blob/master/Documentation/AdvancedUsage.md#adapting-and-retrying-requests