如何在viewDidLoad之前在Swift中初始化AFNEtworking类

Question

I'm new to Swift. Trying to understand how to initialize my AFNetworking class prior to view did load. I'm accessing the class from the ViewController like this

var serverAnalytics = ServerAnalytics()
print(serverAnalytics.today)

Problem is the stored variables in the class from the JSON file do not initialize prior to viewDidload. Therefore the properties are default/blank. Using AFNetworking and SwiftyJSON.

import Foundation

class ServerAnalytics {

    let manager = AFHTTPSessionManager()
    var today:Double! = 0
    var complete:Bool! = false


    init(){
    manager.GET("http://www.somerandomjsonurl",
        parameters: nil,
        progress: nil,
        success: { (operation: NSURLSessionDataTask,responseObject: AnyObject?) in
            if let responseObject = responseObject {
                //print("Response: " + responseObject.description)
                let json = JSON(responseObject)
                 self.today = json["salesdata"]["list"][0]["todays_sales"].double!

            }

        },
        failure: { (operation: NSURLSessionDataTask?,error: NSError) in
            print("Error: " + error.localizedDescription)
        })

    }

}

Answer 1

The basic problem here is that your ServerAnalytics class is populating those values using a network call, meaning that you can't really tell when they're going to be populated - or if they will at all if the network request fails for some reason.

So instead of thinking about how to make sure those values are populated before viewDidLoad runs, think about how to make your view controller do the right thing whether the values are populated or not, and how to have your ServerAnalytics class tell the view controller when the values are ready. Using the delegate pattern, much like UIKit does, seems a good strategy for this.