努力使用 flutter 雲 Firestore 一次更新多個文檔

Question

我一直在為這段代碼苦苦掙扎，我正在為商店開發一個 POS 應用程序，所以我擁有的一個功能是該應用程序能夠注冊添加到購物車的每件商品以及何時進行銷售，我需要通過從我的雲 Firestore 數據庫中的每個項目數量字段中刪除一個單位來更新這些項目，所以我所做的是，每次用戶將項目添加到購物車時，它都會將該文檔的 ID 添加到字符串數組中，例如[4343434343,34343543434]，然后在用戶確認銷售后，我希望它遍歷每個文檔並通過從每個項目文檔中的時間數量字段中刪除數字1來更新字段，我嘗試簡單地通過創建一個帶有 firebase 更新的 for 循環，但出現錯誤，然后我嘗試使用批量寫入來執行此操作，顯然，它應該在處理多個文件時有所幫助，問題是我不斷收到錯誤

未處理的異常：錯誤 state：此批次已提交，無法再更改

它甚至一次都不會更改更新字段中的值，這是我的代碼，我不確定我在這里做錯了什么，但我會為此發瘋。 另外，如果您有替代方法來實現我正在嘗試做的事情，我們將不勝感激，

WriteBatch batch = FirebaseFirestore.instance.batch();
//Create a batch
print(cart_numbers.toString());
Future update() async {
    for (var i = 0; i < cart_numbers.length; i++) {
        print('is iterator wooooooorking !!!!!' + i.toString());
        FirebaseFirestore.instance.collection("items")
            .doc(cart_numbers[i].toString()).get().then((value) {
                print('==============================================' +
                    value.data().toString());
                print('==============================================' +
                    value.data()['quantity'].toString());
                int newer = value.data()['quantity'];
                newer--;
                print('newwwwwwwwwwwwwwwwwwwwwwwwerrrrrrrrrrrrr' + newer.toString());
                batch.update(
                    //Give the ref of document.
                    FirebaseFirestore.instance.collection('items')
                    .doc(cart_numbers[i].toString()),
                    //And the data to add in it.
                    {
                        'quantity': newer
                    }
                );
            });
    }

}

void start() async {
    await update();
    batch.commit();
}

start()

這是調試控制台

is iterator wooooooorking !!!!!0
I/flutter ( 3091): is iterator wooooooorking !!!!!1
I/flutter ( 3091): is iterator wooooooorking !!!!!2
E/EGL_adreno( 3091): tid 3281: eglSurfaceAttrib(1582): error 0x3009 (EGL_BAD_MATCH)
W/OpenGLRenderer( 3091): Failed to set EGL_SWAP_BEHAVIOR on surface 0x81bff820, error=EGL_BAD_MATCH
I/flutter ( 3091): found data on cloudstore Instance of '_MapStream<QuerySnapshotPlatform, QuerySnapshot>'
I/flutter ( 3091): yessssssssssssssssssssssssssssssssssssssssssssssssssss
I/flutter ( 3091): yessssssssssssssssssssssssssssssssssssssssssssssssssss
I/flutter ( 3091): =============================================={name: bobo2012, quantity: 7, price: 5000, category: Antivirus Software, id: 2467046743, productid: 496184004787577}
I/flutter ( 3091): ==============================================7
I/flutter ( 3091): newwwwwwwwwwwwwwwwwwwwwwwwerrrrrrrrrrrrr6
E/flutter ( 3091): [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: Bad state: This batch has already been committed and can no longer be change    

我不斷收到的錯誤

E/flutter ( 4054): #0      int._throwFormatException (dart:core-patch/integers_patch.dart:131:5)
E/flutter ( 4054): #1      int._parseRadix (dart:core-patch/integers_patch.dart:157:16)
E/flutter ( 4054): #2      int._parse (dart:core-patch/integers_patch.dart:100:12)
E/flutter ( 4054): #3      int.parse (dart:core-patch/integers_patch.dart:63:12)
E/flutter ( 4054): #4      Home.update.<anonymous closure>.<anonymous closure>
package:weepay_pos/home.dart:53
E/flutter ( 4054): #5      List.forEach (dart:core-patch/growable_array.dart:302:8)
E/flutter ( 4054): #6      Home.update.<anonymous closure>
package:weepay_pos/home.dart:52
E/flutter ( 4054): #7      _rootRunUnary (dart:async/zone.dart:1198:47)
E/flutter ( 4054): #8      _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter ( 4054): #9      _FutureListener.handleValue (dart:async/future_impl.dart:143:18)
E/flutter ( 4054): #10     Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:696:45)
E/flutter ( 4054): #11     Future._propagateToListeners (dart:async/future_impl.dart:725:32)
E/flutter ( 4054): #12     Future._completeWithValue (dart:async/future_impl.dart:529:5)
E/flutter ( 4054): #13     _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:40:15)
E/flutter ( 4054): #14     _completeOnAsyncReturn (dart:async-patch/async_patch.dart:311:13)
E/flutter ( 4054): #15     Query.get (package:cloud_firestore/src/query.dart)
package:cloud_firestore/src/query.dart:1
E/flutter ( 4054): <asynchronous suspension>
E/flutter ( 4054): #16     Home.update
package:weepay_pos/home.dart:51
E/flutter ( 4054): #17     Home.build.<anonymous closure>.<anonymous closure>.<anonymous closure>.<anonymous closure>
package:weepay_pos/home.dart:1278
E/flutter ( 4054): #18     _rootRunUnary (dart:async/zone.dart:1198:47)
E/flutter ( 4054): #19     _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter ( 4054): #20     _FutureListener.handleValue (dart:async/future_impl.dart:143:18)
E/flutter ( 4054): #21     Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:696:45)
E/flutter ( 4054): #22     Future._propagateToListeners (dart:async/future_impl.dart:725:32)
E/flutter ( 4054): #23     Future._completeWithValue (dart:async/future_impl.dart:529:5)
E/flutter ( 4054): #24     _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:40:15)
E/flutter ( 4054): #25     _completeOnAsyncReturn (dart:async-patch/async_patch.dart:311:13)
E/flutter ( 4054): #26     CollectionReference.add (package:cloud_firestore/src/collection_reference.dart)
package:cloud_firestore/src/collection_reference.dart:1
E/flutter ( 4054): #27     _rootRunUnary (dart:async/zone.dart:1198:47)
E/flutter ( 4054): #28     _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter ( 4054): #29     _FutureListener.handleValue (dart:async/future_impl.dart:143:18)
E/flutter ( 4054): #30     Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:696:45)
E/flutter ( 4054): #31     Future._propagateToListeners (dart:async/future_impl.dart:725:32)
E/flutter ( 4054): #32     Future._completeWithValue (dart:async/future_impl.dart:529:5)
E/flutter ( 4054): #33     _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:40:15)
E/flutter ( 4054): #34     _completeOnAsyncReturn (dart:async-patch/async_patch.dart:311:13)
E/flutter ( 4054): #35     MethodChannelDocumentReference.set (package:cloud_firestore_platform_interface/src/method_channel/method_channel_document_reference.dart)
package:cloud_firestore_platform_interface/…/method_channel/method_channel_document_reference.dart:1
E/flutter ( 4054): #36     _rootRunUnary (dart:async/zone.dart:1198:47)
E/flutter ( 4054): #37     _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter ( 4054): #38     _FutureListener.handleValue (dart:async/future_impl.dart:143:18)
E/flutter ( 4054): #39     Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:696:45)
E/flutter ( 4054): #40     Future._propagateToListeners (dart:async/future_impl.dart:725:32)
E/flutter ( 4054): #41     Future._completeWithValue (dart:async/future_impl.dart:529:5)
E/flutter ( 4054): #42     _AsyncAwaitCompleter.complete (dart:async-patch/async_patch.dart:40:15)
E/flutter ( 4054): #43     _completeOnAsyncReturn (dart:async-patch/async_patch.dart:311:13)
E/flutter ( 4054): #44     MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart)
package:flutter/…/services/platform_channel.dart:1
E/flutter ( 4054): #45     _rootRunUnary (dart:async/zone.dart:1198:47)
E/flutter ( 4054): #46     _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter ( 4054): #47     _FutureListener.handleValue (dart:async/future_impl.dart:143:18)
E/flutter ( 4054): #48     Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:696:45)

Answer 1

不需要實現 for 循環。 只需獲取所有商品並使用forEach() function 檢查商品是否在購物車內。 如果是這樣，請編輯數量字段。

Future update(List<int> cartNumbers) async {
  WriteBatch batch = FirebaseFirestore.instance.batch();

  // 1. Get all items
  // 2. Iterate through each item
  // 3. Parse each document ID
  // 4. Check if cart_numers contains item
  // 5. Change quantity

  FirebaseFirestore.instance.collection("items").get().then((querySnapshot) {
    querySnapshot.docs.forEach((document) {
      try {

        // Only if DocumentID has only numbers
        if (cartNumbers.contains(int.parse(document.id))) {
          batch.update(document.reference,
              {"quantity": document.data()["quantity"] - 1});
        }
      } on FormatException catch (error) {

        // If a document ID is unparsable. Example "lRt931gu83iukSSLwyei" is unparsable.
        print("The document ${error.source} could not be parsed.");
        return null;
      }
    });
    return batch.commit();
  });
}

試試這個例子：

class HomePage extends StatelessWidget {

  // In this case, I manually added the items ids
  final List<int> cartNumbers = [121212, 434343, 565656];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("Items"),
          actions: [
            Center(
                child: Padding(
              padding: const EdgeInsets.only(right: 15),
              child: Text("Quantity"),
            ))
          ],
        ),
        body: StreamBuilder<QuerySnapshot>(
          stream: FirebaseFirestore.instance.collection("items").snapshots(),
          builder: (context, snapshot) {
            if (snapshot.hasData) {
              return Column(
                children: [
                  Expanded(
                    child: ListView.builder(
                      itemCount: snapshot.data.docs.length,
                      itemBuilder: (context, index) {
                        return ListTile(
                          title: Text(snapshot.data.docs[index].id),
                          trailing: Text(
                              snapshot.data.docs[index]["quantity"].toString()),
                        );
                      },
                    ),
                  ),
                  RaisedButton(
                    onPressed: () => update(cartNumbers),
                    child: Text("Update"),
                  ),
                ],
              );
            } else {
              return Center(child: CircularProgressIndicator());
            }
          },
        ));
  }
}