flutter - 如何在 Flutter 中使用带有 arrayContains 列表的 where 查询

Question

Map carsMap = {
    "vehicles": [
      {
        "name": "Vehicle1",
        "models": ["bus", "plane", "bicycle"]
      },
      {
        "name": "Vehicle2",
        "models": ["motorcycle", "sporcar", "plane"]
      },
      {
        "name": "Vehicle3",
        "models": ["motorcycle", "plane", "bicycle"]
      }
    ]
  };

如上所示，我有车辆列表，我想查询并显示哪个列表包括飞机和摩托车。我可以使用此代码单查询哪个列表包括飞机，但我不能同时查询哪个列表包括飞机和摩托车。

List<Map> updatedList = carsList
        .where((m) => m.toString().toLowerCase().contains("plane".toLowerCase()))
        .toList();

顺便说一下，飞机和摩托车只是一个例子，这些数据可以根据用户输入而改变。所以我想根据用户输入动态查询。

我怎么能在 where 查询或其他方式中做到这一点。

这是我使用 Firebase 的源代码。

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';

class Home1 extends StatefulWidget {
  @override
  _Home1State createState() => _Home1State();
}

class _Home1State extends State<Home1> {
  final _firestore = FirebaseFirestore.instance;

  @override
  Widget build(BuildContext context) {
    CollectionReference tarifRef = _firestore.collection("vehicles");

    return Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            StreamBuilder<QuerySnapshot>(
              stream: tarifRef.snapshots(),
              builder: (BuildContext context, AsyncSnapshot asyncsnapshot) {
                if (asyncsnapshot.hasError) {
                  return Center(
                    child: Text("Error"),
                  );
                } else {
                  if (asyncsnapshot.hasData) {
                    List<DocumentSnapshot> listOfDocumentSnapshot =
                        asyncsnapshot.data.docs;
                    return Flexible(
                      child: ListView.builder(
                        itemCount: listOfDocumentSnapshot.length,
                        itemBuilder: (context, index) {
                          return Card(
                            color: Colors.indigo,
                            child: ListTile(
                              title: Text(
                                "${listOfDocumentSnapshot[index]["name"]}",
                                style: TextStyle(
                                  fontSize: 20,
                                  color: Colors.white,
                                ),
                              ),
                              subtitle: Text(
                                "${listOfDocumentSnapshot[index]["vehicleList"]}",
                                style: TextStyle(
                                  fontSize: 15,
                                  color: Colors.white,
                                ),
                              ),
                              trailing: IconButton(
                                icon: Icon(
                                  Icons.delete,
                                  color: Colors.white,
                                ),
                                onPressed: () async {
                                  await listOfDocumentSnapshot[index]
                                      .reference
                                      .delete();
                                },
                              ),
                            ),
                          );
                        },
                      ),
                    );
                  } else {
                    return Center(
                      child: CircularProgressIndicator(),
                    );
                  }
                }
              },
            ),
          ],
        ),
      ),
    );
  }
}

Answer 1

You need a logical OR in your condition :

  List<Map> updatedList = carsMap['vehicles']
      .where((m) =>  m.toString().toLowerCase().contains("plane".toLowerCase())) || 
m.toString().toLowerCase().contains("motorcyle".toLowerCase()))
      .toList();

Also, you can use this

  var carsMap = {
    'vehicles': [
      {
        'name': 'Vehicle1',
        'models': ['bus', 'plane', 'bicycle']
      },
      {
        'name': 'Vehicle2',
        'models': ['motorcycle', 'sporcar', 'plane']
      },
      {
        'name': 'Vehicle3',
        'models': ['motorcycle', 'plane', 'bicycle']
      }
    ]
  };
  var n = carsMap['vehicles'].where((element) =>
      (element['models'] as List).contains('plane') ||
      (element['models'] as List).contains('motorcycle'));

If You Want To Query Dynamically

Add filter keys in the filters list and create a function to check whether the element has a common value with filters or not

  List filters = [
    'motorcycle',
    'plane'
  ];
  filter(e){
    for(var f in filters)
      if(e['models'].contains(f)) return true;
    return false;
  }
  var n = carsMap['vehicles'].where(filter);