Custom Conditions

A simple guide on how to write a custom observer condition.

Sometimes you may have unique requirements for an observer condition. When this is the case you can easily create your own ObserverCondition. The code below comments on how to create your own condition.

// The example below does not have many practical uses
// but it shows the bare minimum needed to create a custom condition.
// This condition makes an object only visible if the connections
// ClientId mathes the serialized value, _id.

// Make a new class which inherits from ObserverCondition.
// ObserverCondition is a scriptable object, so also create an asset
// menu to create a new scriptable object of your condition.
[CreateAssetMenu(menuName = "FishNet/Observers/ClientId Condition", fileName = "New ClientId Condition")]
public class ClientIdCondition : ObserverCondition
{
    /// <summary>
    /// ClientId a connection must be to pass the condition.
    /// </summary>
    [Tooltip("ClientId a connection must be to pass the condition.")]
    [SerializeField]
    private int _id = 0;

    private void Awake()
    {
        // Awake can be optionally used to initialize values based on serialized
        // data. The source file of DistanceCondition is a good example
        // of where Awake may be used.
    }
    
    /// <summary>
    /// Returns if the object which this condition resides should be visible to connection.
    /// </summary>
    /// <param name="connection">Connection which the condition is being checked for.</param>
    /// <param name="currentlyAdded">True if the connection currently has visibility of this object.</param>
    /// <param name="notProcessed">True if the condition was not processed. This can be used to skip processing for performance. While output as true this condition result assumes the previous ConditionMet value.</param>
    public override bool ConditionMet(NetworkConnection connection, bool currentlyAdded, out bool notProcessed)
    {
        notProcessed = false;

        // When true is returned it means the connection meets
        // the condition requirements. When false, the
        // connection does not and will not see the object.

        // Will return true if connection Id matches _id.
        return (connection.ClientId == _id);
    }

    /// <summary>
    /// Type of condition this is. Certain types are handled different, such as Timed which are checked for changes at timed intervals.
    /// </summary>
    /// <returns></returns>
    /* Since clientId does not change a normal condition type will work.
    * See API on ObserverConditionType for more information on what each
    * type does. */
    public override ObserverConditionType GetConditionType() => ObserverConditionType.Normal;
}

You can get an idea of the flexibility of a condition by exploring the source of other premade conditions.