So I am using fabric plugin/Twitter-kit to use twitter api in my application. I want to get the image URL of profile picture of a celebrity. here is my code below.
func getImageURL(celebrity :String) -> String{
var imageURL = ""
let client = TWTRAPIClient()
let statusesShowEndpoint = userSearch
let params = ["q": celebrity,
"page" : "1",
"count" : "1"
]
var clientError : NSError?
let request = client.URLRequestWithMethod("GET", URL: statusesShowEndpoint, parameters: params, error: &clientError)
client.sendTwitterRequest(request) { (response, data, connectionError) -> Void in
if connectionError != nil {
print("Error: \(connectionError)")
}
do {
let json = try NSJSONSerialization.JSONObjectWithData(data!, options: [])
print("json: \(json)")
let profileImageURL: String? = json[0].valueForKey("profile_image_url_https") as? String
imageURL = self.cropTheUrlOfImage(profileImageURL!)
print(imageURL)
//how do i return the value back. confused ?????
return imageURL
} catch let jsonError as NSError {
print("json error: \(jsonError.localizedDescription)")
}
}
return imageURL
}
I don't know how to return value because the method finishes before the closure executes completely. I am new to swift, Any help is appreciated.
I want to use this method in cellForRowIndexPath in tableview to dowload image from imageURl.
You need to return from an @escaping closure. Change the function
func getImageURL(celebrity: String) -> String {
}
to
func getImageURL(celebrity: String, completion: @escaping(String)->()) {
// your code
completion(imgURL)
}
You can use it as given below
getImageURL(celebrity: String) { (imgURL) in
self.imgURL = imgURL // Using self as the closure is running in background
}
Here is an example how I write multiple methods with closures for completion.
class ServiceManager: NSObject {
// Static Instance variable for Singleton
static var sharedSessionManager = ServiceManager()
// Function to execute GET request and pass data from escaping closure
func executeGetRequest(with urlString: String, completion: @escaping (Data?) -> ()) {
let url = URL.init(string: urlString)
let urlRequest = URLRequest(url: url!)
URLSession.shared.dataTask(with: urlRequest) { (data, response, error) in
// Log errors (if any)
if error != nil {
print(error.debugDescription)
} else {
// Passing the data from closure to the calling method
completion(data)
}
}.resume() // Starting the dataTask
}
// Function to perform a task - Calls executeGetRequest(with urlString:) and receives data from the closure.
func downloadMovies(from urlString: String, completion: @escaping ([Movie]) -> ()) {
// Calling executeGetRequest(with:)
executeGetRequest(with: urlString) { (data) in // Data received from closure
do {
// JSON parsing
let responseDict = try JSONSerialization.jsonObject(with: data!, options: .allowFragments) as? [String: Any]
if let results = responseDict!["results"] as? [[String:Any]] {
var movies = [Movie]()
for obj in results {
let movie = Movie(movieDict: obj)
movies.append(movie)
}
// Passing parsed JSON data from closure to the calling method.
completion(movies)
}
} catch {
print("ERROR: could not retrieve response")
}
}
}
}
Below is the example how I use it to pass values.
ServiceManager.sharedSessionManager.downloadMovies(from: urlBase) { (movies : [Movie]) in // Object received from closure
self.movies = movies
DispatchQueue.main.async {
// Updating UI on main queue
self.movieCollectionView.reloadData()
}
}
I hope this helps anybody looking for the same solution.