CODEWITHSUNDEEP
swiftswift2
Wraith
Wraith

Reputation: 491

How send info from class method when dispatch_async(dispatch_get_main_queue()) is runing

I have a ViewController, and after tap button i want get data from web. 

let myClass = Class()
    myClass.myMethod() {
        dispatch_async(dispatch_get_main_queue()) {               
        }
    }

In my Class file i have a method

func myMethod( completion:()->() ) {  
    if let connectToInternetAndGetDataFromWeb
        completion()
    } else {
        print("Cold not construct a valid URL")
        completion()
    }
}

And my class to connect to internet and getting data is 

func downloadJSONFromURL() {
    if let httpResponse {
        switch(httpResponse.statusCode) {
        case 200:
        // 2. Create JSON Object with data
            do { 
                try 
            } catch {
                print(error)
            }
        }             
    } else {
        print("Error: Not a valid HTTP response")            
    }   
    dataTask!.resume()
}

And my question is how sent feedback to ViewController to show alert information from class. If i have internet connection is ok but for example when i give wrong web address i have error print("Error: Not a valid HTTP response") but how can i send this error to ViewController ?

Upvotes: 0

Views: 189

Answers (1)

JulianM
JulianM

Reputation: 2550

There are multiple ways to do this. I think the easiest part for your case is adding a closure parameter in the downloadJSONFromURL(). 

func downloadJSONFromURL(completion:((error:NSError?)->Void)) {
    if let httpResponse {
        switch(httpResponse.statusCode) {
        case 200:
        // 2. Create JSON Object with data
            do { 
                try 
                completion(nil)
            } catch {
                print(error)
                completion(error)
            }
        }             
    } else {
        print("Error: Not a valid HTTP response")            
    }   
    dataTask!.resume()
}

Of course you have to chain the completion closure up to your UIViewController that is making the request. So the myMethodalso gets an optional error parameter in it's closure and so on. In the end you have your UIViewController class like this

let myClass = Class()
    myClass.myMethod() {(error:NSError?) -> Void in
        dispatch_async(dispatch_get_main_queue()) { 
          //Show Alert or whatever is necessary for the error
        }
    }

Upvotes: 0

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