FirebaseUser user; 
void _registerUser(String _email,String _password) async {
    user = (await _auth.createUserWithEmailAndPassword(
      email: _email,
      password: _password,
    )).user;
    if (user != null) {
      // User registered successfully
      //  Add user details in realtime database or cloudfirestore
    } else {
     // User not registered Successfully
    }
  }
}

final FirebaseUser user  
 void _signInWithEmailAndPassword(String _email,String _password) async {
      user   = (await _auth.signInWithEmailAndPassword(
      email: _email,
      password: _password,
    )).user;
    if (user != null) {
      // Login successful
      // Navigate to main page
    } else {
     // Invalid email and password
     // Navigate to registration page
    }
  }
}

Future<void> newGroup() {
    return Firestore.instance.collection("hoge").add({
      "hoge": hogehoge
    });
}

Future<void> editGroup() {
    var db = Firestore.instance;
    return db.collection("group").document(groupID).setData({
      "hoge": hogehoge
    });
  }

Future<void> _uploadImage(String documentId,) async {
    return Firestore.instance
        .collection("group")
        .document(documentId)
        .updateData({"documentId": documentId});
  }

Stream<QuerySnapshot> getGroupItem(String groupId) {
  return Firestore.instance
      .collection("group")
      .document(groupId)
      .get();
}

Future<Group> getGroupInfo(String groupId) async {
    var document = Firestore.instance.collection("group").document(groupId).get();
    return await document.then((doc) {
      return Group.setGroup(doc);
    });
  }
// 呼び出し
var groupInfo = await helper.getGroupInfo(widget.groupId);

Stream<QuerySnapshot> getGroupItem(String groupId) {
  return Firestore.instance
      .collection("group")
      .document(groupId)
      .snapshots();
}

Stream<QuerySnapshot> getGroupItem(String groupId) {
    return Firestore.instance
        .collection("group")
        .orderBy("updated_at", descending: true)
        .snapshots();
  }

Stream<QuerySnapshot> searchGroup(String title) {
    return Firestore.instance
        .collection("group")
        .where("title", isEqualTo: title)
        .snapshots();
    }

Stream<QuerySnapshot> getGroupItem(String groupId) {
      return Firestore.instance
          .collection("group")
          .getDocuments();
    }

Future getData(String collection, String documentId) async {
  DocumentSnapshot docSnapshot =
      await Firestore.instance
        .collection(collection)
        .document(documentId)
        .get();
  return docSnapshot.data;
}

Future<void> removeImage(String groupId) {
    return Firestore.instance
        .collection("group")
        .document(groupId)
        .delete();
  }

 Future<void> removeImage(String groupId, String groupDetailId) {
    return Firestore.instance
        .collection("group")
        .document(groupId)
        .collection("group_item")
        .document(groupDetailId)
        .delete();
  }
```    

### データ有無チェック

```dart
 Query colRef = Firestore.instance
        .collection('user')
        .where('mobile', isEqualTo:_phoneNumber)
        .where('type',isEqualTo:'editor');

    colRef.getDocuments().then((data){
      if(data.documents.isNotEmpty){
         data.documents.forEach((data){
               print(data['Name']);
           });
              Toast.show("authorize User", context, 
                duration: Toast.LENGTH_LONG, gravity: Toast.BOTTOM);
      } else{
        Toast.show("Unauthorize User", context,
            duration: Toast.LENGTH_LONG, gravity: Toast.BOTTOM);
      }
    });