JSON Parsing Error When Fetching Data from Stack Exchange API

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1

I’m having trouble parsing JSON data from a REST API call. When I try to make a network request and convert the response to JSON, I get an error saying the data format is incorrect.

Here’s my code:

override func viewDidLoad() {
    super.viewDidLoad()
    setupSearchInterface()
    
    let apiEndpoint = "https://api.stackexchange.com/2.3/search"
    guard let requestURL = URL(string: apiEndpoint) else { return }
    
    var apiRequest = URLRequest(url: requestURL)
    apiRequest.httpMethod = "GET"
    
    let networkTask = URLSession.shared.dataTask(with: apiRequest) { (responseData, urlResponse, requestError) in
        if let networkError = requestError {
            print("Network error: \(networkError.localizedDescription)")
            return
        }
        
        guard let data = responseData else { return }
        
        do {
            let parsedJSON = try JSONSerialization.jsonObject(with: data) as! [String: Any]
            print(parsedJSON)
        } catch {
            print("JSON parsing failed: \(error.localizedDescription)")
        }
    }
    networkTask.resume()
}

I keep getting parsing errors even though the API should return valid JSON. I heard that some APIs return compressed data but URLSession should handle that automatically. What could be causing this issue?

2

I ran into something similar when working with compressed responses from various APIs. While URLSession does handle standard gzip compression automatically, the Stack Exchange API uses a specific compression format that sometimes causes issues. Try adding explicit headers to your request to ensure you’re getting uncompressed data. Add apiRequest.setValue("application/json", forHTTPHeaderField: "Accept") and apiRequest.setValue("identity", forHTTPHeaderField: "Accept-Encoding") before making the request. Also, print the raw response data as a string first to see what you’re actually receiving - sometimes the API returns HTML error pages instead of JSON when parameters are missing or malformed.

3

I’ve encountered this exact scenario multiple times when integrating various REST APIs. The Stack Exchange API is particularly strict about required parameters - without the mandatory site parameter, it returns an error response wrapped in HTML rather than JSON, which explains your parsing failure. However, there’s another common issue I discovered during my implementations: the API often returns HTTP status codes other than 200 even for legitimate errors, but the response body still contains valid JSON error information. Your current code doesn’t check the HTTP status code before attempting to parse. Consider casting the urlResponse to HTTPURLResponse and examining the statusCode property. When I added this check to my Stack Exchange integrations, it revealed that many “parsing errors” were actually API errors with valid JSON error messages that provided much clearer debugging information than the generic parsing failure messages.

4

yea, the stack exchange api needs params like site to return valid json. your url is missing those, so its prbly sending an error response. add ?site=stackoverflow to your endpoint and that might fix the json parsing error.