Before you begin

Before you can useRealtime Database,you need to:

• Register your Unity project and configure it to use Firebase.

  • If your Unity project already uses Firebase, then it's alreadyregistered and configured for Firebase.

  • If you don't have a Unity project, you can download asample app.

• Add theFirebaseUnity SDK (specifically,FirebaseDatabase.unitypackage) toyour Unity project.

Note that adding Firebase to your Unity project involves tasks both in theFirebase console and in your open Unity project(for example, you download Firebase config files from the console, then movethem into your Unity project).

Saving Data

There are five methods for writing data to theFirebase Realtime Database:

Get a DatabaseReference

To write data to the Database, you need an instance ofDatabaseReference:

usingFirebase;usingFirebase.Database;publicclassMyScript:MonoBehaviour{voidStart(){// Get the root reference location of the database.DatabaseReferencereference=FirebaseDatabase.DefaultInstance.RootReference;}}

Write, update, or delete data at a reference

Basic write operations

For basic write operations, you can useSetValueAsync() to save data to aspecified reference, replacing any existing data at that path. You can use thismethod to pass types that correspond to the available JSON types as follows:

• string
• long
• double
• bool
• Dictionary<string, Object>
• List<Object>

If you use a typed C# object, you can use the built inJsonUtility.ToJson()to convert the object to raw Json and callSetRawJsonValueAsync().For example, you may have a User class that looked as follows:

publicclassUser{publicstringusername;publicstringemail;publicUser(){}publicUser(stringusername,stringemail){this.username=username;this.email=email;}}

You can add a user withSetRawJsonValueAsync() as follows:

privatevoidwriteNewUser(stringuserId,stringname,stringemail){Useruser=newUser(name,email);stringjson=JsonUtility.ToJson(user);mDatabaseRef.Child("users").Child(userId).SetRawJsonValueAsync(json);}

UsingSetValueAsync() orSetRawJsonValueAsync() in this way overwrites dataat the specified location, including any child nodes. However, you can stillupdate a child without rewriting the entire object. If you want to allow usersto update their profiles you could update the username as follows:

mDatabaseRef.Child("users").Child(userId).Child("username").SetValueAsync(name);

Append to a list of data

Use thePush() method to append data to a list in multiuser applications.ThePush() method generates a unique key every time a newchild is added to the specified Firebase reference. By using theseauto-generated keys for each new element in the list, several clients canadd children to the same location at the same time without write conflicts. Theunique key generated byPush() is based on a timestamp, so list items areautomatically ordered chronologically.

You can use the reference to the new data returned by thePush() method to getthe value of the child's auto-generated key or set data for the child. CallingKey on aPush() reference returns the value of theauto-generated key.

Update specific fields

To simultaneously write to specific children of a node without overwriting otherchild nodes, use theUpdateChildrenAsync() method.

When callingUpdateChildrenAsync(), you can update lower-level child values byspecifying a path for the key. If data is stored in multiple locations to scalebetter, you can update all instances of that data usingdata fan-out. For example, agame might have aLeaderboardEntry class like this:

publicclassLeaderboardEntry{publicstringuid;publicintscore=0;publicLeaderboardEntry(){}publicLeaderboardEntry(stringuid,intscore){this.uid=uid;this.score=score;}publicDictionary<string,Object>ToDictionary(){Dictionary<string,Object>result=newDictionary<string,Object>();result["uid"]=uid;result["score"]=score;returnresult;}}

To create a LeaderboardEntry and simultaneously update it to the recent scorefeed and the user's own score list, the game uses code like this:

privatevoidWriteNewScore(stringuserId,intscore){// Create new entry at /user-scores/$userid/$scoreid and at// /leaderboard/$scoreid simultaneouslystringkey=mDatabase.Child("scores").Push().Key;LeaderBoardEntryentry=newLeaderBoardEntry(userId,score);Dictionary<string,Object>entryValues=entry.ToDictionary();Dictionary<string,Object>childUpdates=newDictionary<string,Object>();childUpdates["/scores/"+key]=entryValues;childUpdates["/user-scores/"+userId+"/"+key]=entryValues;mDatabase.UpdateChildrenAsync(childUpdates);}

This example usesPush() to create an entry in the node containing entries forall users at/scores/$key and simultaneously retrieve the key withKey. The key can then be used to create a second entry in the user'sscores at/user-scores/$userid/$key.

Using these paths, you can perform simultaneous updates to multiple locations inthe JSON tree with a single call toUpdateChildrenAsync(), such as how thisexample creates the new entry in both locations. Simultaneous updates made thisway are atomic: either all updates succeed or all updates fail.

Delete data

The simplest way to delete data is to callRemoveValue() on a reference to thelocation of that data.

You can also delete by specifyingnull as the value for another writeoperation such asSetValueAsync() orUpdateChildrenAsync(). You can use thistechnique withUpdateChildrenAsync() to delete multiple children in a single APIcall.

Know when your data is committed.

To know when your data is committed to theFirebase Realtime Database server, youcan add a continuation. BothSetValueAsync() andUpdateChildrenAsync()return aTask that allows you to know when the operation is complete. If thecall is unsuccessful for any reason, the TasksIsFaulted will be true with theException property indicating why the failure occurred.

Save data as transactions

When working with data that could be corrupted by concurrentmodifications, such as incremental counters, you can use atransaction operation.You give this operation aFunc. This updateFunc takes the current stateof the data as an argument and returns the new desired state you would like towrite. If another client writes to the location before your new value issuccessfully written, your update function is called again with the new currentvalue, and the write is retried.

For instance, in a game you could allow users to update a leaderboard withthe five highest scores:

privatevoidAddScoreToLeaders(stringemail,longscore,DatabaseReferenceleaderBoardRef){leaderBoardRef.RunTransaction(mutableData=>{List<object>leaders=mutableData.ValueasList<object>if(leaders==null){leaders=newList<object>();}elseif(mutableData.ChildrenCount>=MaxScores){longminScore=long.MaxValue;objectminVal=null;foreach(varchildinleaders){if(!(childisDictionary<string,object>))continue;longchildScore=(long)((Dictionary<string,object>)child)["score"];if(childScore <minScore){minScore=childScore;minVal=child;}}if(minScore >score){// The new score is lower than the existing 5 scores, abort.returnTransactionResult.Abort();}// Remove the lowest score.leaders.Remove(minVal);}// Add the new high score.Dictionary<string,object>newScoreMap=newDictionary<string,object>();newScoreMap["score"]=score;newScoreMap["email"]=email;leaders.Add(newScoreMap);mutableData.Value=leaders;returnTransactionResult.Success(mutableData);});}

Using a transaction prevents the leaderboard from being incorrect if multipleusers record scores at the same time or the client had stale data. If thetransaction is rejected, the server returns the current value to the client,which runs the transaction again with the updated value. This repeats until thetransaction is accepted or too many attempts have been made.

• Retrieve data from yourRealtime Database
• Learn how to structure data