dart - Unhandled Exception: InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List<dynamic>

Question

I am trying to get the JSON response from the server and output it to the console.

Future<String> login() async {
    var response = await http.get(
        Uri.encodeFull("https://etrans.herokuapp.com/test/2"),
        headers: {"Accept": "application/json"});

    this.setState(() {
      data = json.decode(response.body);
    });


    print(data[0].name);
    return "Success!";
  }

Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'List

What could be the reason?

Answer 1

Here are 2 common ways this could go wrong:

1. If your response is a json object like

   [
       {
         key1: value1,
         key2: value2,
         key3: value3,
       },
       {
         key1: value1,
         key2: value2,
         key3: value3,
       },
   
       .....
   ] 
   

   Then, we use data[0]["name"], not data[0].name Unless we cast to an object that has the name property, we cannot use data[0].name

   We cast like this data = json.decode(response.body).cast<ObjectName>();

   ObjectName can be whatever object you want (Inbuilt or Custom). But make sure it has the name property

2. If your response is a JSON object like

   {
       dataKey: [
         {
           key1: value1,
           key2: value2,
           key3: value3,
         } 
       ] 
   }
   

   Then json.decode will return a Map, not a List

   Map<String, dynamic> map = json.decode(response.body);
   List<dynamic> data = map["dataKey"];
   print(data[0]["name"]);