反序列化来自cloud_firestore数据库的一个非常复杂的JSON对象时遇到一些问题。我已经采取了一种相当漂亮的方式格式化该对象。所以这是它的样子：
{
"mealType": "Breakfast",
"id": 6,
"totalCalories": 187.0,
"nutritionixData": [
{
"phospate": 152.15,
"totalFat": 11.11,
"potassium": 173.4,
"servingQuantity": 3.0,
"photo": {
"thumbnail": "https://d2xdmhkmkbyw75.cloudfront.net/9_thumb.jpg",
"highRes": null
},
"totalCarbohydrate": 0.04,
"calories": 187.0,
"nutrients": [
{
"attributeID": 203,
"value": 20.366
},
{
"attributeID": 204,
"value": 11.1095
},
{
"attributeID": 205,
"value": 0.0425
},
{
"attributeID": 207,
"value": 0.7225
},
{
"attributeID": 208,
"value": 187.0
},
{
"attributeID": 255,
"value": 52.9975
},
{
"attributeID": 268,
"value": 782.0
},
{
"attributeID": 291,
"value": 0.0
},
{
"attributeID": 301,
"value": 11.05
},
{
"attributeID": 303,
"value": 1.3685
},
{
"attributeID": 304,
"value": 17.0
},
{
"attributeID": 305,
"value": 152.15
},
{
"attributeID": 306,
"value": 173.4
},
{
"attributeID": 307,
"value": 60.35
},
{
"attributeID": 309,
"value": 1.4535
},
{
"attributeID": 312,
"value": 0.0604
},
{
"attributeID": 315,
"value": 0.023
},
{
"attributeID": 317,
"value": 13.345
},
{
"attributeID": 318,
"value": 507.45
},
{
"attributeID": 319,
"value": 152.15
},
{
"attributeID": 320,
"value": 152.15
},
{
"attributeID": 401,
"value": 0.34
},
{
"attributeID": 404,
"value": 0.0485
},
{
"attributeID": 405,
"value": 0.1607
},
{
"attributeID": 406,
"value": 5.9764
},
{
"attributeID": 410,
"value": 0.8526
},
{
"attributeID": 415,
"value": 0.289
},
{
"attributeID": 417,
"value": 19.55
},
{
"attributeID": 418,
"value": 0.663
},
{
"attributeID": 431,
"value": 0.0
},
{
"attributeID": 432,
"value": 19.55
},
{
"attributeID": 435,
"value": 19.55
},
{
"attributeID": 501,
"value": 0.2253
},
{
"attributeID": 502,
"value": 0.8449
},
{
"attributeID": 503,
"value": 1.009
},
{
"attributeID": 504,
"value": 1.4841
},
{
"attributeID": 505,
"value": 1.6363
},
{
"attributeID": 506,
"value": 0.5372
},
{
"attributeID": 507,
"value": 0.2729
},
{
"attributeID": 508,
"value": 0.7973
},
{
"attributeID": 509,
"value": 0.652
},
{
"attributeID": 510,
"value": 0.9911
},
{
"attributeID": 511,
"value": 1.2895
},
{
"attributeID": 512,
"value": 0.5848
},
{
"attributeID": 513,
"value": 1.1815
},
{
"attributeID": 514,
"value": 1.8224
},
{
"attributeID": 515,
"value": 2.9801
},
{
"attributeID": 516,
"value": 1.3413
},
{
"attributeID": 517,
"value": 1.0098
},
{
"attributeID": 518,
"value": 0.7327
},
{
"attributeID": 601,
"value": 79.9
},
{
"attributeID": 606,
"value": 3.111
},
{
"attributeID": 610,
"value": 0.0
},
{
"attributeID": 611,
"value": 0.017
},
{
"attributeID": 612,
"value": 0.085
},
{
"attributeID": 613,
"value": 2.278
},
{
"attributeID": 614,
"value": 0.629
},
{
"attributeID": 617,
"value": 3.655
},
{
"attributeID": 618,
"value": 2.108
},
{
"attributeID": 619,
"value": 0.0935
},
{
"attributeID": 620,
"value": 0.102
},
{
"attributeID": 621,
"value": 0.0255
},
{
"attributeID": 626,
"value": 0.612
},
{
"attributeID": 628,
"value": 0.1105
},
{
"attributeID": 629,
"value": 0.0085
},
{
"attributeID": 630,
"value": 0.0
},
{
"attributeID": 631,
"value": 0.017
},
{
"attributeID": 645,
"value": 4.437
},
{
"attributeID": 646,
"value": 2.4225
}
],
"saturatedFat": 3.11,
"serving_weight": 85.0,
"sodium": 60.35,
"foodName": "chicken",
"dietaryFiber": 0.0,
"protein": 20.37,
"cholesterol": 79.9,
"sugar": 0.0
}
],
"meals": "chicken"
}
这是我尝试反序列化此对象的方法：
class FirebaseFood {
int id;
String mealType;
String meals;
List<FireNutritionix> fireNutritionix;
double totalCalories;
FirebaseFood(
{this.fireNutritionix,
this.id,
this.meals,
this.mealType,
this.totalCalories});
factory FirebaseFood.fromFirebase(Map<dynamic, dynamic> parsedFirebase) {
var list = parsedFirebase['nutritionixData'] as List;
List<FireNutritionix> fireNutritionix =
list.map((i) => FireNutritionix.fromFirebase(i)).toList();
return FirebaseFood(
fireNutritionix: fireNutritionix,
id: parsedFirebase['id'],
meals: parsedFirebase['meals'],
mealType: parsedFirebase['mealType'],
totalCalories: parsedFirebase['totalCalories']);
}
}
class FireNutritionix {
double calories;
double cholesterol;
double dietaryFiber;
List<FireNutrients> fireNutrients;
double phospate;
List<FirePhoto> photo;
double potassium;
double protein;
double saturatedFat;
double servingQuantity;
double serving_weight;
double sodium;
double sugar;
double totalCarbohydrate;
double totalFat;
FireNutritionix(
{this.calories,
this.cholesterol,
this.dietaryFiber,
this.fireNutrients,
this.phospate,
this.photo,
this.potassium,
this.protein,
this.saturatedFat,
this.serving_weight,
this.servingQuantity,
this.sodium,
this.sugar,
this.totalCarbohydrate,
this.totalFat});
factory FireNutritionix.fromFirebase(Map<dynamic, dynamic> parsedFirebase) {
var list = parsedFirebase['nutrients'] as List; // being called on null
List<FireNutrients> fireNutrients =
list.map((i) => FireNutrients.fromFirebase(i)).toList();
var list2 = parsedFirebase['photo'] as List; // being called on null
List<FirePhoto> firePhoto = list2.map((i) => FirePhoto.fromFirebase(i));
return FireNutritionix(
calories: parsedFirebase['calories'],
cholesterol: parsedFirebase['cholesterol'],
dietaryFiber: parsedFirebase['dietaryFiber'],
fireNutrients: fireNutrients,
phospate: parsedFirebase['phospate'],
photo: firePhoto,
potassium: parsedFirebase['potassium'],
protein: parsedFirebase['protein'],
saturatedFat: parsedFirebase['saturatedFat'],
serving_weight: parsedFirebase['serving_weight'],
servingQuantity: parsedFirebase['servingQuantity'],
sodium: parsedFirebase['sodium'],
sugar: parsedFirebase['sugar'],
totalCarbohydrate: parsedFirebase['totalCarbohydrate'],
totalFat: parsedFirebase['totalFat']);
}
}
class FireNutrients {
int attributeID;
double value;
FireNutrients({this.attributeID, this.value});
factory FireNutrients.fromFirebase(Map<dynamic, dynamic> parsedFirebase) {
return FireNutrients(
attributeID: parsedFirebase['attributeID'],
value: parsedFirebase['value']);
}
}
class FirePhoto {
String highRes;
String thumbnail;
FirePhoto({this.highRes, this.thumbnail});
factory FirePhoto.fromFirebase(Map<dynamic, dynamic> parsedFirebase) {
return FirePhoto(
highRes: parsedFirebase['highRes'],
thumbnail: parsedFirebase['thumbnail']);
}
}
我得到的错误是：
E/flutter ( 9185): Receiver: null
E/flutter ( 9185): Tried calling: map<FireNutrients>(Closure: (dynamic) => FireNutrients)
E/flutter ( 9185): #0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
E/flutter ( 9185): #1 new FireNutritionix.fromFirebase
package:thesis/fromFirebase/firebaseFood.dart:69
E/flutter ( 9185): #2 _FitnessAppHomeScreenState.checkMealsList.<anonymous closure>.<anonymous closure>
package:thesis/fitnessAppHomeScreen.dart:182
E/flutter ( 9185): #3 List.forEach (dart:core-patch/growable_array.dart:283:8)
虽然我不明白为什么要对null调用parsedFirebase ['Nutritions']。.任何帮助和解释将不胜感激！非常感谢！