type 'int' is not a subtype of type 'String'

Why This Happens

In Dart, implicit type conversions do not happen. When JSON data contains an integer but your code expects a String, this runtime type error occurs. Use .toString() for explicit conversion or check the type before casting.

The Problem

final json = {'id': 123};
final String id = json['id']; // int is not String

The Fix

final json = {'id': 123};
final String id = json['id'].toString();

Step-by-Step Fix

1. 1

   Identify the error

   Look at the error message: type 'int' is not a subtype of type 'String'. This means an int value was assigned to a String variable.

2. 2

   Find the cause

   Check JSON parsing or dynamic data handling where the actual type differs from the expected type.

3. 3

   Apply the fix

   Use .toString() for explicit conversion, or parse the JSON with proper type handling in your fromJson factory.