我有一个名为 company 的集合。 所有公司都将像我的屏幕截图一样存储。

当我添加另一家公司时，我想检查 name 是否已经存在。 如何执行？

这里，“Nova”和“Tradetech”是两家公司。

当我再次尝试添加 "Nova" 字段 name: "nova" 时，我想显示一条通知:“公司已经存在! “。

最佳答案

我已经用下面的代码解决了这个问题，感谢您的帮助!

在我曾经找到的以下代码中

1)文档是否存在？

2) KEY 是否存在？

3)值是否存在？

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),
      ],
    );
  }
}

基于我现有代码的旧的复杂方法 //////////////////////////////////////////////////////

概念

它有一个搜索栏，当你输入时它会显示公司名称，即是否存在

Card 和 RaisedButton。我在 Firestore 中使用小写字母以避免搜索错误。我已使用 toLowercase() 强制将 TextFormField 输出设为小写。您可以将其更改为您自己的文本格式。

代码

//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),)),
              );
          }
        });
  }
}

关于firebase - 检查 Field 是否已经存在于 Flutter Firestore 中，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51122211/