Get items from json data and add to array

Question

I am using the Flickr api to retrieve images based on a search using the following code. The function sends the image id to the endpoint and returns an object which I parse to get a specific url for said image. I get the response that I want but I am trying to get all the image urls which are in item.source and add them to an array. I have tried returning a array but the compiler complains this cannot be done as it's a non-void return from a void method despite me setting [String] as the return. How can I get the list of item.source as an array to be used outside of getURLImages()? Alternatively, I have created urlsList as below, and tried to append the item.source to this but this always prints as empty. For context, I am planning to create a UICollectionView to display said images/urls.

UPDATE

Below is the function from class A that calls getURLImages from class B:

 let result = try JSONDecoder().decode(Response.self, from: data)
  
 if (result.stat == "ok"){
     for urls in result.photos!.photo {           
         DispatchQueue.main.async {
             GetImageInfo().getURLImages(photoId: urls.id) { urlsList in
                  print("Received \(urlsList)")
              }
         }
      }
 }

Below is the function from class B:

let result = try JSONDecoder().decode(Response.self, from: data)
var urlList = [String]()
for item in result.sizes!.size {
    DispatchQueue.main.async {
        if (item.label == "Square"){
            urlList.append(item.source)
                            
        }
    }
 }
 completion(urlList)

How can I access the urlsList property outside the scope of the functions so that it can be implemented into a UICollectionView

Tomas Jablonskis · Accepted Answer · 2021-02-15 14:54:51Z

1

You cannot directly return a value for a function from a closure. You will have to use completion handler closure for this.

Example:

func getURLImages(photoId: String, completion: @escaping ([String]) -> Void) {
    ...
    // Call completion handler when you generate your [String] response
    completion(yourImageURLs)
    ...
}

And use it like this:

let urls = [String]()

getURLImages(photoId: "some id") { [weak self] imageURLs in
    guard let self = self else { return }

    print("Received some \(imageURLs)"
    self.urls = imageURLs
    self.updateCollectionViewOrSomething()
}

func updateCollectionViewOrSomething() {
    self.collectionView.reloadData()
}

edited Feb 15, 2021 at 14:54

answered Feb 15, 2021 at 14:24

Tomas Jablonskis

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9 Comments

Nouman Over a year ago

Inside the function, what would I replace yourImageURLS with? They're currently obtained once looping through the json response and where a specific key,value occurs. Would I do completion(urlsList)?

Tomas Jablonskis Over a year ago

You could create a local [String] array inside your closure before starting your for loop and populate that array instead of urlsList, then use that array inside a completion instead. That way you could easily move your getURLImages somewhere else without breaking your code that much.

Tomas Jablonskis Over a year ago

And to even more isolate your function from outside you could improve your parameters list: getURLImages(photoId: String, config: AppConfig = AppConfig(), completion: ...)

Tomas Jablonskis Over a year ago

This way you could move getURLImages into its separate file or anywhere else in the codebase without breaking your existing code.

Tomas Jablonskis Over a year ago

By the way, completion handler should be called when you FINISH gathering your urls, so, outside the for loop.

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