Firebase: Iterate over map - firebase

Question

I got a collection called "inventar" which contains a doc with an auto generated value which contains a single map I want to iterate about.
Note that the keys are going to vary, because the user is going to specify it.
How can I iterate over this map so that I can output the key and value in my table cells listed below?
new StreamBuilder<QuerySnapshot>(
stream: FirebaseFirestore.instance
.collection("inventar")
.where("verfallsdatum")
.snapshots(),
builder: (BuildContext context,
AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError) {
return Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return Text("Loading");
}
return new Table(
children: [
new TableRow(children: [
new TableCell(child: new Text("Produkt")),
new TableCell(child: new Text("Verfallsdatum")),
]),
// how to iterate here?
new TableRow(
children: [
new TableCell(
child: new Text("key"),
),
new TableCell(
child: new Text("value"),
),
]
)
]);
},
)
Edit:
I am trying to get this data out of my database since alomost one month! Which major mistake or misunderstanding do I have, that I am unable to query single document which contains a map and output it as table? Is this task so awefuly rough to perform or am I just dumb? :D
Here is the recent attampt I did, but it says there is no method "forEach" for the type "DocumentSnapshot" even though I think I say this attampt in pretty much every tutorial. But mine aint work!
var products = await db.collection("inventar").doc("vqQXArtqnFyAlkPC1PHr").get().then((snapshot) => {
snapshot.forEach((doc) => {
})
});

Answer 1

return StreamBuilder(
stream: FirebaseFirestore.instance
.collection("inventar")
.where("verfallsdatum")
.snapshots(),
builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
if (snapshot.hasError) {
return Text('Something went wrong');
}
if (snapshot.connectionState == ConnectionState.waiting) {
return Text("Loading");
}
return ListView(
children: snapshot.data.docs.map((documentSnapshot) {
var _data = documentSnapshot.data();
return _data.map((key, value) {
return new Table(children: [
new TableRow(children: [
new TableCell(child: new Text("Produkt")),
new TableCell(child: new Text("Verfallsdatum")),
]),
// how to iterate here?
new TableRow(children: [
new TableCell(
child: new Text(key),
),
new TableCell(
child: new Text(value),
),
])
]);
}).toList();
}).toList(),
);
},
);