flutter type_error ai_generated true

type 'Null' is not a subtype of type 'int' in type cast

ID: flutter/typeerror-null-not-subtype-int

Also available as: JSON · Markdown · 中文

88%Fix Rate

84%Confidence

1Evidence

2023-05-12First Seen

Version Compatibility

Version	Status	Introduced	Deprecated	Notes
Flutter 3.0	active	—	—	—
Flutter 3.3	active	—	—	—
Flutter 3.7	active	—	—	—

Root Cause

A null value was assigned or returned where a non-nullable int was expected, often due to missing null-safety handling in JSON parsing or API responses.

generic

中文

在期望非空 int 的地方分配或返回了 null 值，通常是由于 JSON 解析或 API 响应中缺少空安全处理。

Official Documentation

https://dart.dev/null-safety

Workarounds

90% success Use null-safe access with a fallback value: int value = (json['field'] as int?) ?? 0;
```
Use null-safe access with a fallback value:
int value = (json['field'] as int?) ?? 0;
```
95% success Use a JSON parsing library like 'json_serializable' with nullable fields defined properly: @JsonKey(name: 'field', defaultValue: 0) int field;
```
Use a JSON parsing library like 'json_serializable' with nullable fields defined properly:
@JsonKey(name: 'field', defaultValue: 0)
int field;
```
85% success Add explicit null checks before casting: if (json['field'] != null) { int value = json['field'] as int; } else { // handle null case }
```
Add explicit null checks before casting:
if (json['field'] != null) {
  int value = json['field'] as int;
} else {
  // handle null case
}
```

中文步骤

Use null-safe access with a fallback value:
int value = (json['field'] as int?) ?? 0;

Use a JSON parsing library like 'json_serializable' with nullable fields defined properly:
@JsonKey(name: 'field', defaultValue: 0)
int field;

Add explicit null checks before casting:
if (json['field'] != null) {
  int value = json['field'] as int;
} else {
  // handle null case
}

Dead Ends

Common approaches that don't work:

Using 'as int' without null check 90% fail
If the value is null, the cast will throw the same error.
Ignoring null-safety and using 'dynamic' instead of 'int' 70% fail
Defeats the purpose of null safety and can lead to runtime type errors elsewhere.
Assuming the API will never return null for that field 80% fail
APIs can change or return null for missing fields; brittle assumption.