How do I resolve a map value called on null - json

Question

I have a contact model that uses maps but the return is null thus causing aysnc suspension. I have tried tried setting these maps to return an empty list but to no avail do I manage to resolve the issue.
ContactModel{
//factory method constructor
emails: List<Email>.from(parsedJson['Emails'].map((x)=>Email.fromJson(x))),
tasks: List<Tasks>.from(parsedJson["Tasks"].map((x) => Tasks.fromJson(x))),
notes: List<Notes>.from(parsedJson["Notes"].map((x) => Notes.fromJson(x))),
}
The error returns as : No such method map called on null. Receiver null
I have tried to resolve the issue by writing it as such
ContactModel{
//factory method constructor
emails: List<Email>.from(parsedJson['Emails'].map((x)=>Email.fromJson(x))).toList() ?? [],
tasks: List<Tasks>.from(parsedJson["Tasks"].map((x) => Tasks.fromJson(x))).toList() ?? [],
notes: List<Notes>.from(parsedJson["Notes"].map((x) => Notes.fromJson(x))).toList() ?? [],
}

Answer 1

You can try null checking the json like so :
ContactModel{
emails: parsedJson['Emails'] != null ? List<Email>.from(parsedJson['Emails'].map((x)=>Email.fromJson(x))).toList() : [],
tasks: parsedJson['Tasks'] != null ? List<Tasks>.from(parsedJson["Tasks"].map((x) => Tasks.fromJson(x))).toList() : [],
notes:parsedJson['Notes'] != null ? List<Notes>.from(parsedJson["Notes"].map((x) => Notes.fromJson(x))).toList() : [],
}

Answer 2

Basically, I always check 2 things when working with JSON types :
You must check your JSON contains the key you're looking for
You must check null value being returned if the key exist.
I recommend you doing this double check like this :
if(parsedJson.isNotEmpty) {
List<dynamic> emails = [];
if (parsedJson.containsKey('Email') && parsedJson['Email'] is List) {
emails = List<Email>.from(parsedJson['Emails'].map((x)=>Email.fromJson(x)))
}
ContactModel({emails: emails});
}
This way, you always make sure you've got the right type, and avoid production error (imagine your API going nuts). It's more verbose, I know, but to me, good code requires accuracy