如何在flutter中访问ModelName / ProviderName的数据表单实例

Posted 2023-02-23

【中文标题】如何在flutter中访问ModelName / ProviderName的数据表单实例

【英文标题】：how to access data form Instance of ModelName / ProviderName in flutter

【发布时间】：2020-04-06 05:11:41

【问题描述】：

我有一个从 API 获取数据的挑战提供程序。我将数据存储在 List<Challenge> 数组中。在挑战屏幕中，我得到了List<Challenge> 数组。现在我得到的是Instance of 'ChallengeModel'。

在ListView.builder()，如果我做challenge[index].title，我会得到空值。

代码如下：

挑战模型：

import 'package:flutter/material.dart';

class ChallengeModel 

  int id;
  int status;
  String title;
  String description;
  String startDate;
  String endDate;

  ChallengeModel(
    @required id,
    @required title,
    @required description,
    @required startDate,
    @required endDate,
    @required status,
  );

在 Provider 中我如何在数组中添加 ChallengeModel 数据：

_challenges.add(
         ChallengeModel(
           id: result['id'],
           title: result['title'],
           description: result['description'],
           startDate: result['start_date'],
           endDate: result['end_date'],
           status: finalStatus,
         )
        );  

挑战屏幕：

@override
  Widget build(BuildContext context) 
    final challengeProvider = Provider.of<ChallengesProvider>(context);
    var challenges = challengeProvider.items;
    print(challenges);
    return ListView.builder(
      itemCount: challenges.length,
      itemBuilder: (BuildContext context, int index) 
        return Container(
          padding: EdgeInsets.symmetric(vertical: 10, horizontal: 20),
          child: Card(
            child: Column(
              children: <Widget>[
                Text(
                  "$challenges[index].title",
                  style: Theme.of(context).textTheme.title,
                ),
              ],
            ),
          ),
        );
      ,
    );
  

API 数据和以上提供者项目的终端打印结果。

flutter: 
   id:3,
   group_id:1,
   title:Demo Challlenge,
   description:<p>lorem epson</p>,
   start_date:2019-12-12 00:00:00,
   end_date:2020-01-13 00:00:00,
   status_id:2,
   creator_id:1,
   moderator_id:1,
   created_at:2019-12-12 14:26:57,
   updated_at:2019-12-12 14:26:57,
   deleted_at:null,
   teams:[
      
         id:1,
         group_id:1,
         name:Havens Blade,
         logo:https://source.unsplash.com/random/200x200,
         status_id:2,
         creator_id:2,
         moderator_id:2,
         created_at:2019-12-11 01:27:16,
         updated_at:2019-12-11 01:27:16,
         deleted_at:null,
         pivot:
            challenge_id:3,
            team_id:1
         
      ,
      
         id:2,
         group_id:1,
         name:Let's Do it, 
         logo: https://source.unsplash.com/random/200x200, 
         status_id: 2, 
        creator_id: 1, 
        moderator_id: 1, 
        created_at: 2019-12-11 14:34:36, 
        updated_at: 2019-12-11 14:34:36, 
        deleted_at: null, 
        
        id: 3, 
        group_id: 1, 
        name: OneMORE, 
        logo: https://source.unsplash.com/random/200x200, 
        status_id: 2, 
        creator_id: 1, 
        moderator_id: 1, 
        created_at: 2019-12-11 14:35:30, 
        updated_at: 2019-12-11 14:35<…>

flutter: --------------------------------------
flutter: challenges final completed
flutter: [Instance of 'ChallengeModel', Instance of 'ChallengeModel', Instance of 'ChallengeModel']

【问题讨论】：

从参考资料中得到答案。缺少的是模型中的 this 关键字。

【参考方案1】：

模型中缺少this 关键字，如下所示。

class ChallengeModel 

  int id;
  int status;
  String title;
  String description;
  String startDate;
  String endDate;

  ChallengeModel(
    @required this.id,
    @required this.title,
    @required this.description,
    @required this.startDate,
    @required this.endDate,
    @required this.status,
  );

由于此.title 或任何其他数据无法访问。