data parsing between flutter and Flask REST API - python-3.x

Question

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
127.0.0.1 - - [23/Jan/2020 11:42:32] "POST /cards HTTP/1.1" 500 -
My code in flutter:
Future<void> addNewCard(NewCard product) async {
const url = 'http://10.0.2.2:5000/cards';
try {
final response = await http.post(
url,
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,
);
print(newProduct);
_newCard.add(product);
// _items.insert(0, newProduct); // at the start of the list
notifyListeners();
} catch (error) {
print(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"],
}
cards.append(new_cards)
return jsonify(cards)

Answer 1

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

Answer 2

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.