Type casting error when using http.get to retrieve data from movie API in Flutter

[WhisperingWind]

I’m working on a Flutter app and encountering an issue with an http request. When trying to fetch movie data from an API, I’m getting a type casting exception. The error says something about ‘_InternalLinkedHashMap<String, Object>’ not being a subtype of ‘Map<String, String>?’. I’ve been trying to fix this but can’t seem to find the issue.

Here’s my API service class for clarity:

class ApiService {
  static Future<Map<String, dynamic>> fetchDataWithParams(String endpoint, Map<String, String> params) async {
    Map<String, dynamic> responseData = {};
    
    final requestHeaders = {
      "accept": "application/json",
      "x-api-key": "YOUR_API_KEY_HERE",
      "x-api-host": "movie-info-api.p.rapidapi.com"
    };
    
    try {
      final requestUri = Uri.https(endpoint, "/", params);
      var apiResponse = await http.get(requestUri, headers: requestHeaders);
      Map<String, dynamic> parsedResponse = json.decode(apiResponse.body);
      responseData['result'] = parsedResponse;
      return responseData;
    } catch (error) {
      responseData['errorMessage'] = 'Request failed: ' + error.toString();
      return responseData;
    }
  }
}

And here’s how I’m calling the function:

Map<String, dynamic> apiResult = {};
Map<String, String> requestParams = {
  'movieId': 'tt12361974',
  'format': 'json',
  'details': 'extended'
};
String apiEndpoint = 'movie-info-api.p.rapidapi.com';
apiResult = await ApiService.fetchDataWithParams(apiEndpoint, requestParams);

The API should return movie details like title, year, rating, plot, cast, and more in JSON format. Can anyone help me figure out what’s causing this casting error?

[SkippingLeaf]

I’ve hit this exact casting issue before. It’s usually about how you handle the parsed JSON data downstream. The error shows you’re trying to cast _InternalLinkedHashMap<String, Object> to Map<String, String>? somewhere after your API call. Your fetchDataWithParams method looks fine - it returns Map<String, dynamic> correctly. The problem’s probably when you access nested objects in the API response. Movie APIs return complex nested stuff where cast members, genres, or production details are objects or arrays, not strings. Check any code where you’re accessing properties from apiResult['result']. If you’re doing Map<String, String> movieDetails = apiResult['result'], that’s where it breaks. Keep everything as Map<String, dynamic> and only cast specific values when you know their types, like String title = movieData['title'] or int year = movieData['year'].

[SpinningGalaxy]

That error’s definitely a nullability problem. You’re probably casting null objects as non-nullable maps when the response comes back. Movie APIs love to return null for fields like ‘director’ or ‘awards’ - I’ve hit this tons of times. Add ? operators when you access nested data, or use .cast<String, dynamic>() instead of direct casting.

[lucasg]

Your type casting error happens because you’re expecting Map<String, String> but getting Map<String, dynamic> from the JSON response. API responses have mixed data types - strings, numbers, booleans, nested objects - not just strings. I hit this same issue when I started with Flutter APIs. The problem kicks in when you try assigning parsed JSON directly to a Map<String, String> variable. Your json.decode() returns Map<String, dynamic>, which is what you want for API responses. Look at where you’re processing apiResult['result']. If you’re casting it to Map<String, String> anywhere, that’s your problem. Movie APIs return integers for year/rating and nested objects for cast info - you can’t treat them as string-only maps. Stick with Map<String, dynamic> and cast individual fields when you need them.