flutter type_error ai_generated true

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

ID: flutter/isolate-message-deserialization

Also available as: JSON · Markdown · 中文

82%Fix Rate

86%Confidence

1Evidence

2023-10-18First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
Flutter 3.13.0	active	—	—	—
Flutter 3.22.0	active	—	—	—
Dart 3.1.0	active	—	—	—

Root Cause

When sending a message between isolates, the data must be serializable and have exact types; a List containing mixed types or untyped lists caused a type cast failure during deserialization.

generic

中文

在隔离区之间发送消息时，数据必须是可序列化的且具有精确类型；包含混合类型或未类型化列表的 List 在反序列化期间导致类型转换失败。

Official Documentation

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

Workarounds

85% success Explicitly cast the list to the expected type before sending. Example: List<int> data = [1, 2, 3]; await isolate.spawn(workerFunction, data); If data comes from a dynamic source, use 'List<int>.from(data)' to ensure type safety.
```
Explicitly cast the list to the expected type before sending. Example:
  List<int> data = [1, 2, 3];
  await isolate.spawn(workerFunction, data);
If data comes from a dynamic source, use 'List<int>.from(data)' to ensure type safety.
```
80% success Use a typed data class that implements 'toMap' and 'fromMap' for serialization. Example: class MyMessage { final List<int> values; MyMessage(this.values); Map<String, dynamic> toMap() => {'values': values}; factory MyMessage.fromMap(Map<String, dynamic> map) => MyMessage(List<int>.from(map['values'])); } Then send the map and deserialize in the isolate.
```
Use a typed data class that implements 'toMap' and 'fromMap' for serialization. Example:
  class MyMessage {
    final List<int> values;
    MyMessage(this.values);
    Map<String, dynamic> toMap() => {'values': values};
    factory MyMessage.fromMap(Map<String, dynamic> map) => MyMessage(List<int>.from(map['values']));
  }
Then send the map and deserialize in the isolate.
```
75% success Ensure the list is created with a concrete type parameter, e.g., 'List<int>.empty(growable: true)' instead of '[]' which defaults to List<dynamic>.
```
Ensure the list is created with a concrete type parameter, e.g., 'List<int>.empty(growable: true)' instead of '[]' which defaults to List<dynamic>.
```

中文步骤

在发送前显式将列表转换为预期类型。示例：
  List<int> data = [1, 2, 3];
  await isolate.spawn(workerFunction, data);
如果数据来自动态源，使用 'List<int>.from(data)' 确保类型安全。

使用实现 'toMap' 和 'fromMap' 的类型化数据类进行序列化。示例：
  class MyMessage {
    final List<int> values;
    MyMessage(this.values);
    Map<String, dynamic> toMap() => {'values': values};
    factory MyMessage.fromMap(Map<String, dynamic> map) => MyMessage(List<int>.from(map['values']));
  }
然后发送 map 并在隔离区中反序列化。

确保使用具体类型参数创建列表，例如 'List<int>.empty(growable: true)' 而不是默认为 List<dynamic> 的 '[]'。

Dead Ends

Common approaches that don't work:

Use 'List<dynamic>' as the type for the message variable 70% fail
The isolate communication protocol requires concrete types; <dynamic> is not concrete and causes the same error when the receiver expects a specific type.
Wrap the message in a Map with string keys to bypass type checking 60% fail
Maps also require concrete type parameters; a Map<String, dynamic> still fails if the receiver expects Map<String, int>.
Set '--no-verify-types' flag in the Dart VM 90% fail
This flag does not exist; type verification is inherent to the isolate protocol and cannot be disabled.