dart - 从函数 'List can'返回类型 'fetchCountries' t的值，因为它的返回类型为 'Future'

Question

我的 Dart 代码有问题。我正在尝试从API提取一些数据，它返回JSON数组。我创建了一个解析JSON的模型。之后，我尝试将获取的数据传递给函数，但出现此错误:“无法从函数'fetchCountries'返回'List类型的值，因为它的返回类型为'Future'”。

有人有线索吗？

国家模型

import 'dart:convert';

List<Country> countryFromJson(String str) => List<Country>.from(json.decode(str).map((x) => Country.fromJson(x)));

class Country {
    String country;
    int cases;
    int todayCases;
    int deaths;
    int todayDeaths;
    int recovered;
    int active;
    int critical;
    int casesPerOneMillion;
    int deathsPerOneMillion;
    int totalTests;
    int testsPerOneMillion;

    Country({
        this.country,
        this.cases,
        this.todayCases,
        this.deaths,
        this.todayDeaths,
        this.recovered,
        this.active,
        this.critical,
        this.casesPerOneMillion,
        this.deathsPerOneMillion,
        this.totalTests,
        this.testsPerOneMillion,
    });

    factory Country.fromJson(Map<String, dynamic> json) => Country(
        country: json["country"],
        cases: json["cases"],
        todayCases: json["todayCases"],
        deaths: json["deaths"],
        todayDeaths: json["todayDeaths"],
        recovered: json["recovered"],
        active: json["active"],
        critical: json["critical"],
        casesPerOneMillion: json["casesPerOneMillion"],
        deathsPerOneMillion: json["deathsPerOneMillion"],
        totalTests: json["totalTests"],
        testsPerOneMillion: json["testsPerOneMillion"],
    );
}

国家服务

import 'dart:async';
import 'package:http/http.dart' as http;
import '../models/country.dart';

Future<Country> fetchCountries() async {
  final response = await http.get('https://coronavirus-19-api.herokuapp.com/countries');

  if(response.statusCode == 200) {
    return countryFromJson(response.body);
  }
  else {
    throw Exception('Failed to load Country')
  }
}

Answer 1

根据您的函数定义，您应该

Future<List<Country>> fetchCountries() async {
  final response = await http.get('https://coronavirus-19-api.herokuapp.com/countries');

  if(response.statusCode == 200) {
    return countryFromJson(response.body);
  }
  else {
    throw Exception('Failed to load Country')
  }
}

因此，您应该等待一个国家/地区列表，而不是一个国家/地区。
希望能帮助到你!