I try to fetch data from firbase but I get this error.The method '[]' can't be unconditionally invoked because the receiver can be 'null' - firebase

Question

'''
QuestionModel getQuestionModelFromDatasnapshot(
DocumentSnapshot questionSnapshot) {
QuestionModel questionModel = new QuestionModel();
questionModel.question = questionSnapshot.data()'question'];
List<String> options = [
questionSnapshot.data()["option1"],
questionSnapshot.data()["option2"],
questionSnapshot.data()["option3"],
questionSnapshot.data()["option4"]
];
options.shuffle();
questionModel.option1 = options[0];
questionModel.option2 = options[1];
questionModel.option3 = options[2];
questionModel.option4 = options[3];
questionModel.correctOption = questionSnapshot.data()["option1"];
questionModel.answered = false;
print(questionModel.correctOption.toLowerCase());
return questionModel;
}
'''

Answer 1

It looks like you're using dart with null safety on and you are accessing a list or map that might be null. It's hard to tell from your code, but I'm guessing the offending line is
questionModel.correctOption = questionSnapshot.data()["option1"];
It might be one of the other [] calls earlier in your code (such as
questionSnapshot.data()["option1"]), but the solution is the same.
The problem is that questionSnapshot.data() might return null, and the compiler is flagging it.
If you are sure the data is not null, you can use the ! operator, like this:
questionModel.correctOption = questionSnapshot.data()!["option1"];
Another solution is a conditional null-safe operator ?, with a default value. In this case, the code would look like this:
questionModel.correctOption = questionSnapshot.data()?["option1"]??"DefaultValue;
But I would recommend checking if the returned data is null. It's easier for others to read and can be logged more easily:
var data = questionSnapshot.data();
if (data != null) {
questionModel.correctOption = data["option1"];
}
else {
//do something in that case
}