Despite the connect() method returning 0 (enum), the function specified in the connection is not called

Question

The subject script:

    extends ColorRect

onready var subject = get_parent().get_node('Page1')

func _ready():
    var error = subject.connect('set_timer', self, 'ad')


func ad():
    print('signal connected')

Answer 1

You are setting the function ad to run when the signal set_timer is emitted (not when it is connected). I cannot find an standard set_timer signal (for reference Timer nodes have a timeout signal, perhaps that is what you want?). I'd suppose it is a custom signal you created. If you are not emitting that signal, Godot will not call ad for you.

To emit a custom signal, in the script attached to the subject (Page1), call emit_signal("set_timer"). See Godot documentation on emit_signal.

The following code is taken from Godot documentation on Sigals:

extends Node2D


signal my_signal


func _ready():
    emit_signal("my_signal")

If you try to emit a signal that does not exist, you will get an error in the console like this one:

emit_signal: Can't emit non-existing signal "set_time".

However, in your case, I believe the signal exist, otherwise, when connecting you would have got the following error:

connect: In Object of type 'ColorRect': Attempt to connect nonexistent signal 'set_time' to method 'ColorRect.ad'