_on_RigidBody2D_body_entered signal doesn't work

Question

For a side scroller game i need variuous scene ( main , player , weapon, enemy ).
In the script of the main one, I instance them with "add_child" and they spawn correctly on the screen with their variables.
Now i want to add collision to player, bullet and enemy that are all RigidBody2D with their CollisionShape2D.

This is the code for the Enemy

extends RigidBody2D

var life = 250

func _ready():
    get_node("Timer").start()
    pass
func _on_weapon_body_entered(body):
    if body.is_in_group("weapon"):
        life=life-body.damage
    else:
        life=life+1
    pass


func _on_Timer_timeout():
    get_node("Label").text=String(life)
    get_node("Timer").start()
    pass

In the weapon scene there is a group called weapon

What is the problem?

Answer 1

First thing first, is the onweaponbodyentered() connected to anything? Maybe share the project so we get some context?

Comments

Is connected to the father RigidBody2D (so the enemy)

Here's the project:
https://mega.nz/#!e1kG0ArB!q_SdQuB4QpMXhiCLYhL3AKsYecIiy35QBbNaNkBtqVs