Best way to test vallid links in feed using Swift or Objective-C

Question

I am building a feed with links to multimedia assets. If a link is bad it should not be in the feed as a video that does not play or image that does not load is a poor user experience. The feed is pulled by the phone via JSON from an endpoint without the benefit of a websocket.

I can test the links before putting them in the feed, however, waiting to verify a link takes time and if the feed has many items, I'm anticipating slow loading times.

Even accepting the delay for validating links, I am struggling with how to implement asynchronous calls to the links inside a synchronous conversion process once we have downloaded the data.

Here is the workflow.

1. Asynchronously import JSON as object. You get a JSON object such as:

   {"feed":[{"title":"Check out this video","videosurl":"https://www.youtube.com/somevideo.mp4"}]}

2. Serialize JSON into Array of feed objects (synchronous)

3. Save the array of Feed objects to Core Data (synchronous)

4. Display the objects using an NSFetchedResultsController. (synchronous)

Inside 3-just before saving each item to Core Data would seem like a logical place to test/validate the links.

Here is my code so far inside of Step 3 (changed to use function B)

-(void) saveFeed:(NSArray *)items inContext: (NSManagedObjectContext*) context
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Videofeed" inManagedObjectContext:context];
    items* item;
    for (i=0;i<max;i++){ 
        item = items[i];
NSString * link = item.videosurl;
    __block BOOL validFile = NO;
        [link foundValidFileAtSurlWithCompletion:^(BOOL __validFile) {
                   
          
                     }];
                if (validFile!=YES) {
                  //  continue;//skip this one
                }
                
            NSManagedObject *record = [[NSManagedObject alloc] initWithEntity:entity insertIntoManagedObjectContext:context];
            [record setValue:title forKey:@"title"];
            [record setValue:videosurl forKey:@"videosurl"];
        }
        [context save]
    };//save context
}

Function A

@objc public extension NSString {
    
    @available(iOS 13.0.0, *)
    func fileExists(at surl: NSString) async throws -> Bool {
        let str = self as String
            
        guard let url =  URL(string: str) else { return false }
           
        var request = URLRequest(url: url)
        request.httpMethod = "HEAD"
        request.timeoutInterval = 1.0 // Adjust to your needs
        let (_, response) = try await URLSession.shared.data(for: request)
        return (response as? HTTPURLResponse)?.statusCode == 200
     }
}

Edit:

I have implemented the following code that uses a completionHandler to check for a valid URL and it returns a BOOL of yes or no, however, I don't have a way to hold up the synchronous code to wait for a response. How can I do this from Objective-C?

Function B

@objc public extension NSString {
func foundValidFileAtSurl(completion:@escaping (Bool) -> ()) {
       
        let str = self as String
     
        if (self == "") {
            completion(false)
        }
        if let url = URL(string: str) {
            
            var request = URLRequest(url: url)
            request.httpMethod = "HEAD"//confirm header not complete file
            request.timeoutInterval = 1.0 // Adjust to your needs
            let task = URLSession.shared.dataTask(with: request) {
                data,response,error  in
                guard error == nil else { print(error ?? "error",error!.localizedDescription); return }
                guard data != nil else { print("Empty data"); return }
               // flag = ((response as? HTTPURLResponse)?.statusCode == 200)
                completion((response as? HTTPURLResponse)?.statusCode == 200)
            }
            task.resume()
        }
    }
}

Answer 1

Swift Approach

if let url = URL(string: "https://example.com") {
    // The URL is valid, you can proceed with further checks.
    debugPrint("Valid URL format")
} else {
    debugPrint("Invalid URL format")
}

Objective-C Approach

NSString *urlString = @"https://example.com";
NSURL *url = [NSURL URLWithString:urlString];

if (url && url.scheme && url.host) {
    NSLog(@"Valid URL format");
} else {
    NSLog(@"Invalid URL format");
}