检查Flutter Firestore中是否已存在字段

Question

我有一个名为的收藏company。所有公司都将像我的屏幕快照中那样存储。

当我添加其他公司时，我想检查是否name已经存在。如何执行？

在这里，“ Nova”和“ Tradetech”是两家公司。

当我尝试再次在该字段中添加“ Nova”name: "nova"时，我想显示一个通知：“公司已经存在！” 。

Answer 1

您可以简单地使用where查询来仅接收具有该查询的文档，name然后检查是否获取了文档。这是async将执行您想知道的内容的示例方法。

示例方法

Future<bool> doesNameAlreadyExist(String name) async {
  final QuerySnapshot result = await Firestore.instance
    .collection('company')
    .where('name', isEqualTo: name)
    .limit(1)
    .getDocuments();
  final List<DocumentSnapshot> documents = result.documents;
  return documents.length == 1;
}

如您所见，我仅收到name字段与给定匹配的文档name。我还要补充一点limit(1)，以确保我不会不必要地检索超过1个文档（理论上永远不会发生），然后我只检查集合length中所有文档的in company是否等于1。如果等于1，则已经有一个公司使用该名称，否则不使用。

您也可以删除limit(1)和进行检查documents.length > 1，这也可以，但是可能会检索不必要的文档。

示例实施

@override
Widget build(BuildContext context) {
  return FutureBuilder(
    future: doesNameAlreadyExist('nova'),
    builder: (context, AsyncSnapshot<bool> result) {
      if (!result.hasData)
        return Container(); // future still needs to be finished (loading)
      if (result.data) // result.data is the returned bool from doesNameAlreadyExists
        return Text('A company called "Nova" already exists.');
      else
        return Text('No company called "Nova" exists yet.');
    },
  );
}

在这里，我没有显示错误消息，使用示例方法也很容易实现。但是，使用build了一些小部件的方法。例如，这可以在对话框中工作，但我决定这样做以使其简单易懂。该FutureBuilder发生在doesNameAlreadyExist，在这种情况下，一个名为“新星”从你的问题，并会在年底，返回一个Text小部件，说明名字是否已经存在。

小心

该where查询区分大小写。这意味着如果您键入例如“ noVa”而不是“ nova”，则该检查将不起作用。因为这对您可能很重要，所以您可以使用这个不错的方法，在该方法中，您将创建一个不敏感的额外字段，例如，所有字母都很小，然后您将像这样简单查询：

.where('name_insensitive', isEqualTo: name.toLowerCase())

Answer 2

I have solved this issue with the follwoing code, thanks for helping me!

IN THE FOLLOWING CODE I USED TO FIND

1)A DOCUMENT IS EXISTING OR NOT?

2)A KEY IS EXISTING OR NOT?

3)A VALUE IS EXISTING OR NOT?

SIMPLE METHOD
//////////////////////////////////////////////////////////////////////


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

String myText1 = 'temp1';
String myText2 = 'temp2';
String myText3 = 'temp3';
String myText4 = 'temp4';
String myText5 = 'temp5';
String myText6 = 'temp6';
StreamSubscription<DocumentSnapshot> subscription;
final DocumentReference documentReference =
    Firestore.instance.document("company/Nova");

class Clean extends StatefulWidget {
  @override
  _CleanState createState() => _CleanState();
}

class _CleanState extends State<Clean> {
  @override
  void initState() {
    super.initState();
    subscription = documentReference.snapshots().listen((datasnapshot) {
      //FINDING A SPECIFICDOCUMENT IS EXISTING INSIDE A COLLECTION

      if (datasnapshot.exists) {
        setState(() {
          myText1 = "Document exist";
        });
      } else if (!datasnapshot.exists) {
        setState(() {
          myText2 = "Document not exist";
        });
      }

      //FINDING A SPECIFIC KEY IS EXISTING INSIDE A DOCUMENT

      if (datasnapshot.data.containsKey("name")) {
        setState(() {
          myText3 = "key exists";
        });
      } else if (!datasnapshot.data.containsKey("name")) {
        setState(() {
          myText4 = "key not exists";
        });
      }


      //FINDING A SPECIFIC VALUE IS EXISTING INSIDE A DOCUMENT

      if (datasnapshot.data.containsValue("nova")) {
        setState(() {
          myText5 = "value exists";
        });
      } else if (!datasnapshot.data.containsValue("nova")) {
        setState(() {
          myText6 = "value not exists";
        });
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: <Widget>[
        new Text(myText1),
        new Text(myText2),
        new Text(myText3),
        new Text(myText4),
        new Text(myText5),
        new Text(myText6),
      ],
    );
  }
}

MY OLD COMPLEX METHOD BASED ON MY EXISTING CODE ////////////////////////////////////////////////////////

Concept

it has a search bar,when you type it will show the company name ie existing or not in

一Card和RaisedButton。为了避免搜索错误，我在Firestore中使用小写字母。我已将TextFormField输出强制为小写toLowercase()。您可以将其更改为自己的文本格式。

码

//if the name is not existing it will show a raised button so u can clcik on that to 
//go to a COMPANY ADDING PAGE,otherwise it will only show a **CARD** so that you  
//can't go to the next page to add your company


//code:

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

const blue = 0xFF3b78e7;
String filter = '';
StreamSubscription<DocumentSnapshot> subscription;

final TextEditingController _usercontroller = new TextEditingController();

class CheckAvail extends StatefulWidget {
  @override
  HomeState createState() => HomeState();
}

class HomeState extends State<CheckAvail> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      resizeToAvoidBottomPadding: false,
      body: Column(
        mainAxisAlignment: MainAxisAlignment.start,
        children: <Widget>[
// CHILD1
          new Flexible(
            child: StreamBuilder(
              stream: Firestore.instance
                  .collection('company')
                  .where('name', isGreaterThanOrEqualTo: filter.toLowerCase())
                  .limit(1)
                  .snapshots(),
              builder: (BuildContext context,
                  AsyncSnapshot<QuerySnapshot> snapshot) {
                if (!snapshot.hasData) {
                  return new Column(
                    children: <Widget>[
                      new Card(
                        elevation: 5.0,
                        child: new Image.asset('assets/progress.gif'),
                      )
                    ],
                  );
                } else {
                  return FirestoreListView1(documents: snapshot.data.documents);
                }
              },
            ),
          ),

          new Card(
            elevation: 0.0,
            color: Colors.white,
            shape: new RoundedRectangleBorder(
                borderRadius: BorderRadius.circular(60.0)),
            child: Container(
              padding: new EdgeInsets.only(left: 8.0),
              child: new TextField(
                controller: _usercontroller,
                onChanged: (String z) {
                  setState(() {
                    filter = z;
                  });
                },
                decoration: const InputDecoration(
                  hintText: "Search...",
                  hintStyle: TextStyle(
                      fontFamily: 'roboto',
                      color: Colors.black38,
                      fontSize: 16.0,
                      letterSpacing: -0.500),
                  fillColor: Colors.white,
                  border: InputBorder.none,
                ),
              ),
            ),
          ),
        ],
      ),
      backgroundColor: Color(blue),
    );
  }
}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class FirestoreListView1 extends StatelessWidget {
  final List<DocumentSnapshot> documents;
  FirestoreListView1({this.documents});
  @override
  Widget build(BuildContext context1) {
    return ListView.builder(
        itemCount: documents.length,
        padding: new EdgeInsets.all(1.0),
        itemBuilder: (BuildContext context1, int index) {
          String name = documents[index].data['name'];
          if (name.contains(filter.toLowerCase()) &&
              name.length == filter.length) {
            return new Container(
              padding: new EdgeInsets.only(top: 45.0),
              child: new Card(
                  child: new Text(
                      "Error:Already a Company Exists with this name\nTry another name")),
            );
          } else {
            return (filter.length >= 1)
                ? new Container(
                    padding: new EdgeInsets.only(top: 15.0),
                    child: new RaisedButton(
                      onPressed: () => Navigator.push(
                          context1,
                          new MaterialPageRoute(
                              builder: (context1) => new NextPage(
                                    value1: name,
                                  ))),
                      disabledColor: Colors.white,
                      child: new Text(
                        "Good!You can use this company name",
                      ),
                    ),
                  )
                : new Container(padding: new EdgeInsets.only(top: 250.0),
                child: new Card(child: new Text("CHECK IF YOUR COMPANY NAME \n           AVAILABLE OR NOT",style: new TextStyle(fontSize: 20.0),)),
              );
          }
        });
  }
}

Answer 3

final QuerySnapshot result =
    await Firestore.instance.collection('users').where('nickname', isEqualTo: 
    nickname).getDocuments();

final List < DocumentSnapshot > documents = result.documents;

if (documents.length > 0) { 

  //exists

} else {  

  //not exists

}

Answer 4

使用该功能：

snapshot.data!.data()!.containsKey('key_name')

检查文档中是否存在某个字段。

附言。我刚刚在我的代码 RN 中使用了它并且它有效