How can we increase or decrease an integer value by 1.

[VikashSRathore]

Suppose I have a firebase node named "Likes" that contains integer values. How can I increase or decrease the value of this key by one without fetching the value of the key.

Fetching the key may create problem like :

=> user1 fetches value = 10 => user2 fetches value = 10 => user1 increases value by 1 = 11 => user2 increases value by 1 = 11

Now database will have 11 as final value but if 2 users have incremented value after 10 then it should be 12.

I hope the problem is clear.

I am using Realtime firebase database.

[bezysoftware]

That isn't possible with this library

[bomosura]

Hi, I got good news for you, it is possible with this library! Here is my sample of it

Based on their documentation: https://firebase.google.com/docs/reference/rest/database#section-server-values

public async Task Run()
{
    var firebaseClient = new FirebaseClient(
            "<Your URL here>",
            new FirebaseOptions
            {
                AuthTokenAsyncFactory = () => GetAccessToken(),
                AsAccessToken = true
            });

    var dataTest = new CountTest()
    {
        Counts = FieldValue.Increment(1)
    };

    await firebaseClient
        .Child("TestCount")
        .PatchAsync(dataTest);
}

private async Task<string> GetAccessToken() //Source: https://github.com/step-up-labs/firebase-database-dotnet/issues/221#issuecomment-704583145
{
    var jsonString = await File.ReadAllTextAsync("Creds\\firebaseCredential.json");

    var credential = GoogleCredential.FromJson(jsonString).CreateScoped(new string[] {
        "https://www.googleapis.com/auth/firebase.database",
        "https://www.googleapis.com/auth/userinfo.email"
    });

    ITokenAccess c = credential;
    return await c.GetAccessTokenForRequestAsync();
}

public class CountTest
{

    public ServerValue Counts { get; set; }

}

public class FieldValue
{
    public static ServerValue Increment(long value)
    {
        return new ServerValue(new FieldValueIncrement(value));
    }

    public class FieldValueIncrement
    {
        public FieldValueIncrement(long value)
        {
            increment = value;
        }
        public long increment { get; private set; }
    } 
}

public class ServerValue
{
    public ServerValue(object value)
    {
        Value = value;
    }

    [JsonProperty(".sv")]
    public object Value { get; set; }
}

If you want to "Decrease" the integer by 1, just use FieldValue.Increment(-1)

Let me know if this works for you

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[stale[bot]]

Closing the issue due to inactivity. Feel free to re-open