class Reg_Result { final int id; const Reg_Result({required this.id}); factory Reg_Result.fromJson(Map<String, dynamic> json) { return Reg_Result(id: json['user_id']); } }**your text

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Null is not a subtype of int.

CodePudding user response：

First make sure if your id is coming or not, seems like your id is not coming that's why it is showing error

CodePudding user response：

The code you provided is correct. The problem I think is where you are giving calling the class and giving the id, this error means you're id received a null value, not an int. It will be better if you can provide the code of where the class is called.