flutter - Json int双重解析Flutter

Question

问题是我想从此解析:{“cost”:0}翻倍。所以我现在有:

json ['cost']。toDouble()，错误:未处理的异常:NoSuchMethodError:类'String'没有实例方法'toDouble'。

int.parse(json ['cost'])。toDouble()，错误:未处理的异常:类型'int'不是类型'String'的子类型

json ['cost']，错误:未处理的异常:类型'int'不是类型'double'的子类型

完整代码:

factory ShippingMethod.fromJson(Map<String, dynamic> json) {
    dynamic cost = json['cost'];
    print(cost.runtimeType);  // printing runtime type and I get it twice!
    return ShippingMethod(
      code: json['code'],
      title: json['title'],
      description: json['description'],
      cost: cost.toDouble(),
      taxClassId: json['tax_class_id'],
    );
  }

并打印:

I/flutter (  480): int    // first it gives me int 
I/flutter (  480): String  // second it gives me String
E/flutter (  480): [ERROR:flutter/lib/ui/ui_dart_state.cc(166)] Unhandled Exception: NoSuchMethodError: Class 'String' has no instance method 'toDouble'.
E/flutter (  480): Receiver: "0"
E/flutter (  480): Tried calling: toDouble()

另外，这是我从服务器获得的内容:

...
"pickup": {
                        "code": "pickup.pickup",
                        "title": "Standard",
                        "description": "If the cost of the order ...",
                        "cost": 0,
                        "tax_class_id": 0,
                        "text": "0.00 TMT"
                    }
...

Dart让我开心!..是bug还是什么？

Answer 1

将字符串转换为 double ，我们有一个函数:double.parse(String)

json["cost"]返回一个int值，因此我们应该将其转换为字符串，然后将其传递给“double.parse(String)”。

解决方案代码:

double.parse(json["cost"].toString());