GameObject.SendMessage() in Unity 5.5

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from: Unity 5.x By Example by Alan Thorn

SendMessage  function lets you call any other public function on any component attached to the object by specifying the function name as a string. If no function of a matching name exists, then nothing happens for that component. This is a quick and easy way to run customized behavior on an object in a type-agnostic way without using any polymorphism.

The disadvantage is that SendMessage  internally uses a process called Reflection , which is slow and performance-prohibitive. For this reason, SendMessage  should be used infrequently only for death events and similar events, but not frequently, such as every frame.

from: https://docs.unity3d.com/ScriptReference/GameObject.SendMessage.html

public void SendMessage(string methodName, object value= null, SendMessageOptions options= SendMessageOptions.RequireReceiver);

Parameters

  • methodName : The name of the method to call.
  • value : An optional parameter value to pass to the called method.
  • options : Should an error be raised if the method doesn’t exist on the target object?

Description

Calls the method named methodName  on every MonoBehaviour  in this game object.

The receiving method can choose to ignore the argument by having zero parameters. If options is set to SendMessageOptions.RequireReceiver  an error is printed if the message is not picked up by any component.

Note that messages will not be sent to inactive objects (ie, those that have been deactivated in the editor or with the SetActive  function).

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour
{
    void ApplyDamage(float damage) {
        print(damage);
    }
    void Example() {
        gameObject.SendMessage("ApplyDamage", 5.0f);
    }
}