将Firestore DocumentSnapshot转换为Flutter中的地图 [英] Convert Firestore DocumentSnapshot to Map in Flutter
问题描述
我需要使用Flutter在Firestore中使用嵌套数组更新文档.
I need to update a document with nested arrays in Firestore with Flutter.
因此，我需要将整个文档放入地图中，在"sections"数组中对地图进行重新排序，然后将数据存储回文档中.
So I need to get the full document into a Map, reorder the maps in the "sections" array, and then store the data back into the document.
但是我不熟悉如何将快照(DocumentSnapshot)的数据获取到Map中.
I'm however unfamiliar how I can get the data of the snapshot (DocumentSnapshot) into a Map.
下面的示例对我尝试实现的目标无效:
Below an example that doesn't work of what I try to achieve:
final Map<String, dynamic> doc = snapshot.data as Map<String, dynamic>;
"snapshot.data"包含文档的值.该文档的结构如下所示:
"snapshot.data" contains the values of the document. The structure of the document looks like this:
{
name: "Course 1"
sections: [
{name: "Section 1"},
{name: "Section 2"}
]
}
sections数组中的Maps重新排序后，我需要将数据保存回文档中.
Once the Maps in the sections array have been re-ordered, I need to save the data back into the document.
- 问题1:如何将snapshot.data的内容读取到Map中?
- 问题2:是否要删除文档，然后重新添加?还是可以只更新所有内容?
这里是完整功能.相关代码在"onDragFinish"中.
Here the full function. Relevant code is in "onDragFinish".
// Build editable list with draggable list tiles and swipe to delete
List<Widget> buildListViewEdit() {
final course = db.collection("school").document("3kRHuyk20UggHwm4wrUI")
.collection("course").document("74UsE9x7Bsgnjz8zKozv").snapshots();
return [
StreamBuilder(
stream: course,
builder: (context, snapshot) {
if (!snapshot.hasData) return const Text("Loading...");
return Expanded(
child: DragAndDropList(
snapshot.data["sections"].length,
itemBuilder: (context, index) {
return Card(
child: ListTile(
title: Text(snapshot.data["sections"][index]["name"]),
onTap: () {
print("hello");
}
)
);
},
onDragFinish: (before, after) {
print('on drag finish $before $after');
//final docString = snapshot.data.toString();
final Map <String, dynamic> doc = snapshot.data;
//final tempSections = List.castFrom(snapshot.data["sections"]).toList();
//Map data = tempSections[before];
//tempSections.removeAt(before);
//tempSections.insert(after,data);
//snapshot.data["sections"] = tempSections;
//db.collection("school").document("3kRHuyk20UggHwm4wrUI")
//.collection("course").document("74UsE9x7Bsgnjz8zKozv").updateData(snapshot.data);
//var line = snapshot.data["sections"][before];
//snapshot.data["sections"].removeAt(before);
//snapshot.data["sections"].insert(after,line);
/*
List<Map> sections = docCopy["sections"];
Map data = docCopy["sections"][before];
sections.removeAt(before);
sections.insert(after, data);
print(sections);
*/
},
canDrag: (index) {
print('can drag $index');
return index != 3;
},
canBeDraggedTo: (one, two) => true,
dragElevation: 8.0,
)
);
}
)
];
}
尝试将snapshot.data复制到另一个变量时出错:
Error when trying to copy snapshot.data into another variable:
flutter: ══╡ EXCEPTION CAUGHT BY GESTURE LIBRARY ╞═══════════════════════════════════════════════════════════
flutter: The following assertion was thrown while routing a pointer event:
flutter: type 'DocumentSnapshot' is not a subtype of type 'Map<String, dynamic>'
flutter:
flutter: Either the assertion indicates an error in the framework itself, or we should provide substantially
flutter: more information in this error message to help you determine and fix the underlying cause.
flutter: In either case, please report this assertion by filing a bug on GitHub:
flutter: https://github.com/flutter/flutter/issues/new?template=BUG.md
flutter:
flutter: When the exception was thrown, this was the stack:
flutter: #0 _SectionScreenState.buildListViewEdit.<anonymous closure>.<anonymous closure> (package:teach_mob/screens/section_screen.dart:150:45)
工作示例
感谢您的协助.这是一个对我有用的完整示例:
Thanks all for your assistance. Here a full example that worked for me:
// Build editable list with draggable list tiles and swipe to delete
List<Widget> buildListViewEdit() {
final course = db.collection("school").document("3kRHuyk20UggHwm4wrUI")
.collection("course").document("74UsE9x7Bsgnjz8zKozv").snapshots();
return [
StreamBuilder(
stream: course,
builder: (context, snapshot) {
if (!snapshot.hasData) return const Text("Loading...");
return Expanded(
child: DragAndDropList(
snapshot.data["sections"].length,
itemBuilder: (context, index) {
return Card(
child: ListTile(
title: Text(snapshot.data["sections"][index]["name"]),
onTap: () {
print("hello");
}
)
);
},
onDragFinish: (before, after) {
print('on drag finish $before $after');
// Convert AsyncSnapshot to DocumentSnapshot and then
// create a map that can be changed and updated.
final Map <String, dynamic> doc = snapshot.data.data;
// Convert fixed length list to dynamic list, because items in
// fixed length lists can't be added / removed.
final tempSections = List.castFrom(doc["sections"]).toList();
// Get the data of the list item to be dragged
// Remove the data from the current position
// Add the data to the new position of the list
Map data = tempSections[before];
tempSections.removeAt(before);
tempSections.insert(after,data);
// Overwrite sections with new list array
doc["sections"] = tempSections;
// Store the data back into the firestore document
db.collection("school")
.document("3kRHuyk20UggHwm4wrUI")
.collection("course")
.document("74UsE9x7Bsgnjz8zKozv")
.updateData(doc);
},
canDrag: (index) {
print('can drag $index');
return index != 3;
},
canBeDraggedTo: (one, two) => true,
dragElevation: 8.0,
)
);
}
)
];
}
推荐答案
根据我们的讨论快照，它不是DocumentSnapshot，而是AsyncSnapshot
As per our discussion snapshot is not a DocumentSnapshot it is AsyncSnapshot
要获取DocumentSnaphot，请使用snapshot.data
to get the DocumentSnaphot use snapshot.data
要获取实际地图，可以使用snapshot.data.data
to get the actual map you can use snapshot.data.data
这篇关于将Firestore DocumentSnapshot转换为Flutter中的地图的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
