Am looking at the data structure in this post and want to know how you would go about getting the emails of users who belong to a certain group when they could belong to several groups and the GroupID stored against that user is the current group they are participating in?
Do you store the email addresses with the userid under the "members" or, instead, for each member of the group, get that user's email address from the "users" document userid (this would mean iterating through the group/members collection and doing a query for each user. Not very efficient).
Am used to SQL so this is all new to me.
You should have a single node for each user
/users/UID/emails/
/users/UID/emailunread/
/users/UID/settings/
/users/UID/details/
/users/UID/payments/
So you can simply do a subscription for a singular node path this.myDatasubscription = this.DB.list('users/' + this.uid).snapshotChanges() ensuring changes like new emails or account settings will detected and rolled out in real time back to the app, so your are using angular/ng or something similar client side then your variables {{this.email_list}} should update real time with no page changes.
Take a look at this one.
error: Property 'getChildren' does not exist on type 'DataSnapshot'
Related
I am using firebase as a backend for my Android App. And this app is a social media app where users can post, comment & like. so I am storing user data in user_collection and this collection is secured by security rules where if uid == auth.uid (any user can only access data of himself).
Now in this app when a user post something every user can see this post. And in post_collection I am saving userId in post_doc.
So the problem is I need to show name of user to other users and I have only userId but the problem is a user can't get name of other user by uid beacuse of security rules. now I have to solutions for this please tell me which one is better or you can also suggest any other solutions also?
I can use cloud functions getUserNameById() (Problem : I need to call this function very frequently in feed when user scroll)
I can store name also in post_doc (problem : when user changes his name then It will show old name in old post)
Thanks for you kind help
In a scenario like the one you describe, I would typically store the user name in each post doc. I would also ignore updates to the name, as I think of the user name in the post doc as a historical value: this is the name the user had when they posted this. Now you may want different behavior of course, in which case I recommend reading: How to write denormalized data in Firebase
Your approach with Cloud Functions is fine too, and quite common in some situations. But I tend to only use Cloud Functions for reading data, it the read operation itself is particularly complex, which isn't the case here. In a case like this, I'd recommend coming up with a data model that allows the use-case and security you want.
For example: if you create a collection usernames where each document has the UID as its document ID, and then contains a single field with the username for that UID, you could implement the lookup of the user name through Firestore.
So you could have:
Store the full user profile in /users/$uid.
Store the user name in /usernames/$uid.
Have a Cloud Function that triggers when /users/$uid is written and that updates /usernames/$uid.
The client then has read access to each /usernames/$uid document, or even to the entire /usernames collection in one go if needed.
This way the names can be cached on the client, and continue to work when the app is offline, unlike in your approach with a Cloud Function that looks up the user name.
Consider the solution: whatever public data you need (author name, author userpic link etc) just save it with the post at the time it had created.
So your Message Pojo will looks like:
id
authorName
text
etc..
and just display this name (authorName).
It will be the bad way to go any time to User_collection folder to take the name even if there are would be not strict security (becouse it takes time and document reads)
I am doing the user authentication where I have this case:
Read from vendor_type document and if it returns null(doesn't exist) then continue the transaction,
Create new user using .auth().createUserWithEmailAndPassword(email,password),
Read the new users ID,
Write to vendor_type document some of the new user's detail such as name, surname, userId -->> userId is the problem, how can I create a user and get the ID within a single transaction, can I even do that? ,
Take the newly created ID of the user, and create a new vendor document with that ID.
So far I don't have any code to post because I don't know if this is even gonna work so I didn't start. If you have any idea how to implement this, please let me know. The main issue is getting the user ID while still in the transaction.
At the time of writing, it is not possible to combine in one transaction the creation of a user through the createUserWithEmailAndPassword() method from the Auth service AND a write to the Firestore service.
They are two different services offered by Firestore and therefore you cannot combined calls to these two different services in one transaction.
I am working in a small project that uses Firestore database as a backend. I explain about the database so it is understood what I need:
Basically I have a collection that contains a list of documents where each one of them represent a game. For each game I have the name, cover image, info, category, etc.
I also have a collection of the users, where I have the specific UID for each user (retrieved from the auth section), email, etc.
What I want now is to save the score that some user may have in some of these games, as well as the favorite games that the user could save. What I don't get to understand is how to create the connection between the users and the games. For example, I thought that I should save the users score creating a collection within each document(game) in the first collection that mentioned. But when I create this collection with ID "scores" it asks me for the first document where I have to facilitate an ID (if not automatic) and then I don't know how to proceed.
I have read also that I would have to create additional collections in the root folder like "favorites" or "scores" specifying the UID of the user but, how do I connect the user UID, the score, and game which the user got that score from?
I hope I explained myself properly. Thanks.
Firstly, I agree with Doug's comment above. The Firestore tutorial videos are a great resource!
In terms of connecting data to your user, you have some options. You can either:
Create sub-collections under each user. Such as /users/{user_id}/favorites. Favorites could be a sub-collection or an array of game_ids depending on your use case.
Store a userID field in the documents in a top level "scores" or "favorites" collection. Then you can query for scores in the /scores collection by adding a where userID == {user_id} clause to your query of the /scores collection.
I'm working on a project where I have to handle unregistered user - users that have been added to the group but still they do not have registered in the app.
What I'm doing now is to create a new child in my 'user' db, putting all the info that i know about this unregistered user.
Of course, it also has an id.
This id will be used to represent that user and so it will be used in a lot of places of the db.
The problem comes when this user tries to register itself. Since when creating a new user it's not possible to force the 'id' that he already had, Firebase will create a new id for him.
Then, in the db I need to change all the references of the 'old id' with the new one.
Is there any better way to do it ?
1) You can use another "fake" table to remap the IDs, that is, instead of changing the old id and its references you can add new instance to your "fake" table when user registered. And when needed using simple service you can find the corresponding id.
2) Secondly, you can do authentication yourself, what I mean is that, you can develop your own registration service and define the id yourself in registration. If system is already big and hard to change. First option would be suitable but will have some cost in terms of time.
I'm designing a chat app much like Facebook Messenger. My two current root nodes are chats and users. A user has an associated list of chats users/user/chats, and the chats are added by autoID in the chats node chats/a151jl1j6. That node stores information such as a list of the messages, time of the last message, if someone is typing, etc.
What I'm struggling with is where to make the definition of which two users are in the chat. Originally, I put a reference to the other user as the value of the chatId key in the users/user/chats node, but I thought that was a bad idea incase I ever wanted group chats.
What seems more logical is to have a chats/chat/members node in which I define userId: true, user2id: true. My issue with this is how to efficiently query it. For example, if the user is going to create a new chat with a user, we want to check if a chat already exists between them. I'm not sure how to do the query of "Find chat where members contains currentUserId and friendUserId" or if this is an efficient denormalized way of doing things.
Any hints?
Although the idea of having ids in the format id1---||---id2 definitely gets the job done, it may not scale if you expect to have large groups and you have to account for id2---||---id1 comparisons which also gets more complicated when you have more people in a conversation. You should go with that if you don't need to worry about large groups.
I'd actually go with using the autoId chats/a151jl1j6 since you get it for free. The recommended way to structure the data is to make the autoId the key in the other nodes with related child objects. So chats/a151jl1j6 would contain the conversation metadata, members/a151jl1j6 would contain the members in that conversation, messages/a151jl1j6 would contain the messages and so on.
"chats":{
"a151jl1j6":{}}
"members":{
"a151jl1j6":{
"user1": true,
"user2": true
}
}
"messages":{
"a151jl1j6":{}}
The part where this gets is little "inefficient" is the querying for conversations that include both user1 and user2. The recommended way is to create an index of conversations for each user and then query the members data.
"user1":{
"chats":{
"a151jl1j6":true
}
}
This is a trade-off when it comes to querying relationships with a flattened data structure. The queries are fast since you are only dealing with a subset of the data, but you end up with a lot of duplicate data that need to be accounted for when you are modifying/deleting i.e. when the user leaves the chat conversation, you have to update multiple structures.
Reference: https://firebase.google.com/docs/database/ios/structure-data#flatten_data_structures
I remember I had similar issue some time ago. The way how I solved it:
user 1 has an unique ID id1
user 2 has an unique ID id2
Instead of adding a new chat by autoId chats/a151jl1j6 the ID of the chat was id1---||---id2 (superoriginal human-readable delimeter)
(which is exactly what you've originally suggested)
Originally, I put a reference to the other user as the value of the chatId key in the users/user/chats node, but I thought that was a bad idea in case I ever wanted group chats.
There is a saying: https://en.wikipedia.org/wiki/You_aren%27t_gonna_need_it
There might a limitation of how many userIDs can live in the path - you can always hash the value...