[Flutter/dart] Precautions when saving Map data in firestore

Overview

I use firebase's cloud firestore to store my app's data.

This time, I wanted to save the Map data in the firestore, but there were some precautions.

Note 1: key is String

It seems that the Map key that can be saved must be a String type. I wanted to save the Map data with int key, but I have no choice but to convert it to a String .

Note 2: Output from the forestore is not Map type

When retrieving data from the firestore, the type is _internalLinkedHashMap instead of Map type. If you try to assign this to a Map type variable, then exception

_InternalLinkedHashMap<dynamic, dynamic>' is not a subtype of type 'Map<String, dynamic>

occurs.

To assign to a Map type variable, do as follows.

Map<String, int> data= Map<String, int>.from(snapshot.data[key]);