I am trying to POST request from my flutter application to the Flask REST API, testing API with POST MAN has no problem, but on flutter I am getting error in flutter like this:

I/flutter ( 6378): FormatException: Unexpected character (at character 1) I/flutter ( 6378): I/flutter ( 6378): ^

and in Flask APP like this:

[2020-01-23 11:42:32,517] ERROR in app: Exception on /cards [POST] Traceback (most recent call last): File "/home/shaukat/.local/lib/python3.7/site-packages/flask/app.py", line 2311, in wsgi_app response = self.full_dispatch_request() File "/home/shaukat/.local/lib/python3.7/site-packages/flask/app.py", line 1834, in full_dispatch_request rv = self.handle_user_exception(e) File "/home/shaukat/.local/lib/python3.7/site-packages/flask/app.py", line 1737, in handle_user_exception reraise(exc_type, exc_value, tb) File "/home/shaukat/.local/lib/python3.7/site-packages/flask/_compat.py", line 36, in reraise raise value File "/home/shaukat/.local/lib/python3.7/site-packages/flask/app.py", line 1832, in full_dispatch_request rv = self.dispatch_request() File "/home/shaukat/.local/lib/python3.7/site-packages/flask/app.py", line 1818, in dispatch_request return self.view_functionsrule.endpoint File "/home/shaukat/Projects/udemy flask rest API and python/rest-api-sections-master/section3/app.py", line 19, in create_card 'id': request_data["id"], TypeError: 'NoneType' object is not subscriptable - - [23/Jan/2020 11:42:32] "POST /cards HTTP/1.1" 500 - My code in flutter:

Future<void> addNewCard(NewCard product) async {
const url = '';
try {
  final response = await http.post(
    body: json.encode({
      'id': product.id,
      'cardNo': product.cardNo,
      'cardType': product.cardType,
      'amount': product.amount,
  final newProduct = NewCard(
    id: json.decode(response.body)['id'],
    cardNo: product.cardNo,
    cardType: product.cardType,
    amount: product.amount,
  // _items.insert(0, newProduct); // at the start of the list
} catch (error) {
  throw error;

code in python Flask:

@app.route('/cards', methods=['POST'])
def create_card():
    request_data = request.get_json()
    new_cards = {
        'id': request_data["id"],
        'cardNo': request_data["cardNo"],
        'cardType': request_data["cardType"],
        'amount': request_data["amount"],
   return jsonify(cards)

Solution 1: Ethan K

line 19, in create_card 'id': request_data["id"], TypeError: 'NoneType' object is not subscriptable

As you see the server is unable to get the data / parse it. I'd suggest to debug it inside the REST server and check if you are even receving the values.. I understand that postman works for you, but once you understand what are you even getting @ the server it will be easier to fix what flutter sends. my guess is that product.id (flutter code) is an int and not a string.. please send a more detailed debug information to help resolve this. good luck.

Solution 2: Shaukat hussain

I eventually found the solution in a comment of this post Flutter POST request body not sent

I had to add headers: {"Content-Type": "application/json"} in my post request. thanks for your help