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?

Solution 1

Here are 2 common ways this could go wrong:

1. If your response is a json array 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"]);
   

Solution 2

You can use new Map<String, dynamic>.from(snapshot.value);

Solution 3

As doesn't change the type, it's just an assertion.

You need to use:

map['eventType'].cast<String, dynamic>() or

Map<String, dynamic>.from(map['eventType'])

You can also solved by this way:

Map<String, dynamic> myMap = Map<String, dynamic>.from(/*Your Source*/ );

Solution 4

Easiest way (one dimensional):

Map<String, dynamic> data = new Map<String, dynamic>.from(json.decode(response.body));

print(data['name']);

Solution 5

You are trying to case an Instance of InternalLinkedHashMap which is not possible.

You should Serialize and deserialize it back to Map<String, dynamic>.

InternalLinkedHashMap<String, dynamic> invalidMap;

final validMap =
        json.decode(json.encode(invalidMap)) as Map<String, dynamic>;

View more solutions

Comments

[AKASH MATHWANI]

use response.body instead of snapshot.value

[Rajesh]

he used snippet for firebasedatabase

[Admin]

This worked for me..1) Create a List Data ,2) Use Map to decode the json file ,3) Use the List object Data to fetch the name of the json files.4) With the help of index and the list object i have printed the items dynamically from the json file.

[Llama]

give some more details

[Blanc Chen]

i got the same issue. do you mind to check it? stackoverflow.com/questions/67564553/…

[Rammehar Sharma]

and how we convert List<dynamic> to List<Map<String, dynamic>

[AMAL MOHAN N]

@Diyen Momjang, my array is like datakey:[{key:value}, {key:value}, {key:value}] and I'm facing the same issue, can you help me out?

[AK IJ]

check api response formate. e.x => var decode= json.decoder(response.body)