Flutter encode and decode class fails - json

Question

I have a problem. I created the following class:
enum WeatherType {
#JsonValue("sunny")
sunny,
#JsonValue("raining")
raining
}
class Location {
final String locationName;
final String adres;
final num? distance;
final num windSpeed;
final num windDirection;
final String windIconColor;
final num temperature;
final WeatherType weatherType;
TimeOfDay? arrivalTime;
Location(
{required this.locationName,
required this.adres,
required this.windSpeed,
required this.windDirection,
required this.temperature,
required this.weatherType,
required this.windIconColor,
this.distance});
Location.fromJson(Map<String, dynamic> json)
: locationName = json['locationName'],
adres = json['adres'],
distance = json['distance'],
windSpeed = json['windSpeed'],
windDirection = json['windDirection'],
windIconColor = json['windIconColor'],
temperature = json['temperature'],
weatherType = json['weatherType'],
arrivalTime =
TimeOfDay.fromDateTime(DateTime.parse(json['arrivalTime']));
Map<String, dynamic> toJson() {
return {
'locationName': locationName,
'adres': adres,
'distance': distance,
'windSpeed': windSpeed,
'windDirection': windDirection,
'windIconColor': windIconColor,
'temperature': temperature,
'weatherType': weatherType.toString(),
'arrivalTime': arrivalTime.toString(),
};
}
}
When I store this class as JSON string in the localstorage, it gets stored like this:
{"locationName":"Castricum aan Zee","adres":"Strand, 1901 NZ Castricum","distance":4,"windSpeed":12,"windDirection":90,"windIconColor":"76E648","temperature":5,"weatherType":"WeatherType.raining","arrivalTime":"TimeOfDay(23:20)"}
Then when I use the following line of code:
Location test = Location.fromJson(jsonDecode(json));
The app freezes when running that fromJson method. What am I doing wrong in the encoding/decoding of my class?

Answer 1

check for null in arrivalTime
From Json:
json['arrivalTime'] == null
? null
: DateTime.parse(json['arrivalTime'] as String),
To Json:
'arrivalTime': instance.reviewDate?.toIso8601String(),
Enum
enum WeatherType {
sunny,
raining
}
From JSON:
WeatherType deserializedWeatherType = WeatherType.values.byName(jsonValue);
To JSON:
String jsonValue = weatherType.name;

Answer 2

It's most likely because of the way you're decoding arrivalTime - When you encode arrival time, you encode it as a string: "TimeOfDay(23:20)". Then, when you decode it, you're using DateTime.parse(), which doesn't know how to parse that string.
To make your encoding compatible with your decoding, you can encode and decode the TimeOfDay in a more granular way:
Location.fromJson(Map<String, dynamic> json)
: locationName = json['locationName'],
adres = json['adres'],
distance = json['distance'],
windSpeed = json['windSpeed'],
windDirection = json['windDirection'],
windIconColor = json['windIconColor'],
temperature = json['temperature'],
weatherType = json['weatherType'],
arrivalTime = TimeOfDay(
hour: json['arrivalTime']['hour'],
minute: json['arrivalTime']['minute'],
);
Map<String, dynamic> toJson() {
return {
'locationName': locationName,
'adres': adres,
'distance': distance,
'windSpeed': windSpeed,
'windDirection': windDirection,
'windIconColor': windIconColor,
'temperature': temperature,
'weatherType': weatherType.toString(),
'arrivalTime': {
'hour': arrivalTime.hour,
'minute': arrivalTime.minute,
},
};
}