flutter type_error ai_generated true

Unhandled exception: IsolateSpawnException: Failed to deserialize message: type 'List<dynamic>' is not a subtype of type 'List<String>' in type cast

ID: flutter/deserialize-list-subtype-error

Also available as: JSON · Markdown · 中文
92%Fix Rate
89%Confidence
1Evidence
2024-11-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
Flutter 3.10.0 active — — —
Flutter 3.16.0 active — — —
Flutter 3.22.0 active — — —

Root Cause

When spawning an isolate, the message sent contains a List without explicit type information, and the receiving isolate expects a typed list (e.g., `List<String>`), causing a type cast failure during deserialization.

generic

中文

在生成隔离时，发送的消息包含没有显式类型信息的List，而接收隔离期望一个类型化列表（例如`List<String>`），导致反序列化期间的类型转换失败。

Official Documentation

https://api.flutter.dev/flutter/dart-isolate/Isolate/spawn.html

Workarounds

  1. 95% success Explicitly cast the list to the expected type before sending: `isolate.send(list.cast<String>())`. 
    Explicitly cast the list to the expected type before sending: `isolate.send(list.cast<String>())`.
  2. 90% success Define the list with explicit type annotations: `List<String> myList = ['a', 'b'];` and then send it. 
    Define the list with explicit type annotations: `List<String> myList = ['a', 'b'];` and then send it.
  3. 85% success Use a custom class to wrap the data and ensure proper serialization: `class MyData { final List<String> items; MyData(this.items); }`. 
    Use a custom class to wrap the data and ensure proper serialization: `class MyData { final List<String> items; MyData(this.items); }`.

中文步骤

  1. Explicitly cast the list to the expected type before sending: `isolate.send(list.cast<String>())`.
  2. Define the list with explicit type annotations: `List<String> myList = ['a', 'b'];` and then send it.
  3. Use a custom class to wrap the data and ensure proper serialization: `class MyData { final List<String> items; MyData(this.items); }`.

Dead Ends

Common approaches that don't work:

  1. 65% fail

    This only creates a new List<dynamic>; the receiving side still needs a typed list.

  2. 50% fail

    While this works, it adds overhead and is unnecessary; the proper fix is to type the list correctly.

  3. 70% fail

    This avoids the immediate error but may cause other type issues later.