I need to update a document with nested arrays in Firestore with Flutter.
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.
I'm however unfamiliar how I can get the data of the snapshot (DocumentSnapshot) into a Map.
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" contains the values of the document. The structure of the document looks like this:
{
name: "Course 1"
sections: [
{name: "Section 1"},
{name: "Section 2"}
]
}
Once the Maps in the sections array have been re-ordered, I need to save the data back into the document.
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,
)
);
}
)
];
}
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)
Working example
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,
)
);
}
)
];
}
As per our discussion snapshot is not a DocumentSnapshot
it is AsyncSnapshot
to get the DocumentSnaphot use snapshot.data
to get the actual map you can use snapshot.data.data
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