Alamofire nonblocking connection

问题

I am using Alamofire for basic networking. Here is my problem. I have a class

class User {
    var name:String?
    var company:String

init () {
  //
   manager = Alamofire.Manager(configuration: configuration)
  }

 func details () {
    //first we login, if login is successful we fetch the result

 manager.customPostWithHeaders(customURL!, data: parameter, headers: header)
          .responseJSON { (req, res, json, error) in
              if(error != nil) {
                  NSLog("Error: \(error)")
            }
             else {
                 NSLog("Success: \(self.customURL)")
                 var json = JSON(json!)
                 println(json)
                     self.fetch()
                      println("I fetched correctly")
                 }
   }

func fetch() {

   manager.customPostWithHeaders(customURL!, data: parameter, headers: header)

            .responseJSON { (req, res, json, error) in
                if(error != nil) {
                    NSLog("Error: \(error)")
                }
                else {
                    NSLog("Success: \(self.customURL)")
                    var json = JSON(json!)
                    println(json)
            //set name and company
      }
   }
}

My problem is if I do something like

var my user = User()
user.fetch()
println("Username is \(user.name)")

I don’t get anything on the console for user.name. However if I put a break point, I see that I get username and company correctly inside my fetch function. I think manager runs in separate non blocking thread and doesn’t wait. However I really don’t know how can I initialize my class with correct data if I can’t know whether manager finished successfully. So how can I initialize my class correctly for immediate access after all threads of Alamofire manager did their job?

回答1:

You don't want to do the networking inside your model object. Instead, you want to handle the networking layer in some more abstract object such as a Service of class methods. This is just a simple example, but I think this will really get you heading in a much better architectural direction.

import Alamofire

struct User {
    let name: String
    let companyName: String
}

class UserService {

    typealias UserCompletionHandler = (User?, NSError?) -> Void

    class func getUser(completionHandler: UserCompletionHandler) {
        let loginRequest = Alamofire.request(.GET, "login/url")
        loginRequest.responseJSON { request, response, json, error in
            if let error = error {
                completionHandler(nil, error)
            } else {
                println("Login Succeeded!")

                let userRequest = Alamofire.request(.GET, "user/url")
                userRequest.responseJSON { request, response, json, error in
                    if let error = error {
                        completionHandler(nil, error)
                    } else {
                        let jsonDictionary = json as [String: AnyObject]
                        let user = User(
                            name: jsonDictionary["name"]! as String,
                            companyName: jsonDictionary["companyName"]! as String
                        )

                        completionHandler(user, nil)
                    }
                }
            }
        }
    }
}

UserService.getUser { user, error in
    if let user = user {
        // do something awesome with my new user
        println(user)
    } else {
        // figure out how to handle the error
        println(error)
    }
}

Since both the login and user requests are asynchronous, you cannot start using the User object until both requests are completed and you have a valid User object. Closures are a great way to capture logic to run after the completion of asynchronous tasks. Here are a couple other threads on Alamofire and async networking that may also help you out.

Handling Multiple Network Calls
Returning a Value with Alamofire

Hopefully this sheds some light.

来源：https://stackoverflow.com/questions/28972847/alamofire-nonblocking-connection

标签

swift

alamofire