如何使用 flutter 向 firebase 中的现有文档添加字段？

Question

I want to add a new field in an existing Document my firestore collection

so I want to add Field like this:

"name" : "john",
"uid" : "ddddddddddddddddd",
"email" : "example@example.com",
"imageUrl" : "url"

"cart" : {          >>>>>> this field I want to add 
  "Productone":{
  "product name" : "productname", 
  "price" : "50"
    }
  "Productow":{
  "product name" : "productname",  
  "price" : "50"
    }
}

How can I do this so when the user adds a product to the cart, I can store it in firestore?

Answer 1

await FirebaseFirestore.instance.collection('Users').doc(userId)
.update({"cart":
  "Productone":
  {"product name" : "productname", 
  "price" : "50"}
  "Productow":
  {"product name" : "productname",  
  "price" : "50"}
  });

It's explained extremely well here . I believe that Firebase, specifically Flutter documentation is probably one of the best written documentations online. Props to the team.

Answer 2

Firestore can accept map so 'cart' should be added as map:

Map<String, Map<String, dynamic>> cart = {
'Productone'{
"product name" : "productname", 
  "price" : "50"
}
}

 FirebaseFirestore.instance.collection('orders').add({
         orders: cart,
        );

or

FirebaseFirestore.instance.collection('Users').doc(userId)
.update{ 
        orders: cart,
       );

Main Idea is to convert cart to Map specifically Map<String, Map<String, dynamic>>

Answer 3

You can do it using FieldValue .

FirebaseFirestore.instance
    .collection('Users')
    .doc('here is your document uid')
    .update({
  'cart': FieldValue.arrayUnion([
    {
      'Productone': {
        'product name': 'productname',
        'price': '50',
      },
    },
    {
      'Productow': {
        'product name': 'productname',
        'price': '50',
      },
    },
  ]),
});

It will work like List.add

---

One-time data reading:

FutureBuilder<firestore.DocumentSnapshot>(
  future: firestore.FirebaseFirestore.instance
      .collection('Users')
      .doc('your document uid')
      .get(),
  builder: (context, asyncSnapshot) {
    if (asyncSnapshot.hasData) {
      if (asyncSnapshot.data!.exists) {
        return Text(asyncSnapshot.data!.data()!['cart']);
      } else {
        return const Text('Document doesn\'t exist');
      }
    } else {
      return const CircularProgressIndicator();
    }
  });

Realtime changes reading:

StreamBuilder<firestore.DocumentSnapshot>(
  stream: firestore.FirebaseFirestore.instance
      .collection('Users')
      .doc('your document uid')
      .snapshots(),
  builder: (context, asyncSnapshot) {
    if (asyncSnapshot.hasData) {
      if (asyncSnapshot.data!.exists) {
        return Text(asyncSnapshot.data!.data()!['cart']);
      } else {
        return const Text('Document doesn\'t exist');
      }
    } else {
      return const CircularProgressIndicator();
    }
  });

---

Some links:

Official FieldValue class documentation

FlutterFireFieldValue , one-time read , realtime changes

Stack Overfolw answer