Http.put does not accept any but a String - http

Question

Simple is, that I am trying to make a PUT request to my API but I get the type error of:
_CastError (type 'List<String>' is not a subtype of type 'String' in type cast)
My API accepts an Array of strings (string[]), which I know work because I am currently consuming it on the sibling web platform. So I am trying to replicate that on the Flutter app with the below code. At the moment it is just static code.
I know, that the http module is only accept string but is there a way to get around this? As it does not make sense, as what happens if we want to post an int, bool or <List<String>>. I know you can obviously convert using .toString() but my API has certain validation and is rigid on what it can accept.
Code below:
When I use this payload it works because it follows the rigid types of the Http module (<String, String>)
Map<String, String> payloadThatWorks = {"first_name": "First Name"};
Now when I want to give the payload of the type Map<String, List<String>> with the code below:
Map<String, List<String>> payload = {
"personal_settings": ["allow-notification-discussion-mentions"]
};
It throws the error of _CastError (type 'List<String>' is not a subtype of type 'String' in type cast)
in the http.put function below:
Main API Helper function
static Future<http.Response> queryPut(String apiPath, {dynamic body}) async {
SharedPreferences prefs = await SharedPreferences.getInstance();
String accessToken = prefs.getString('access_token');
var response = await http.put(
Uri.encodeFull(_urlBase + '$apiPath'),
body: body,
headers: {
HttpHeaders.authorizationHeader: "Bearer $accessToken",
'Accept': 'application/json'
},
);
return response;
}
However, when helper function is called in my Widget...
http.Response response =
await ApiService.queryPut('/api/users/$username', body: payload);
So i'm in a spot where the http module does not accept anything put <String> but the API does not accept anything but an Array or <List<String>>
How can I get round this or understand why the http put method is so rigid?
Thank you in advance :)
Sam

Answer 1

You can import dart:convert and use its jsonEncode to convert your map or array of map into a string
So basically you will have to do the following
String payloadStr = jsonEncode(payload)
and use this payloadStr to pass in the http methods. Similarly you can use JsonDecoder to convert json string to Map or Array of map.