access variable between dynamic created Objects from library

k2 name main timeline: instance3

This is expected for dynamically created objects. You need to give the instance a name when creating it, or it will generate one for you. Since this was the 3rd object on stage, it becomes "instance3".

Solution:

var k2:kloc2 = new kloc2();
k2.name = "myK2";
trace("My k2.name = " + k2.name);  // My k2.name = myK2

k2 demo_tekst before: null

Writing MovieClip(root) simply datatypes the root as a MovieClip object (which it already is). You can simplify this by writing:

root.k2.demo_tekst

However, while you may have a property called "k2" on your root object (a.k.a. MainTimeline), you don't have DisplayList object by that name. The DisplayList and the properties on an object are two distinctly separate things. In your case, there is a property on root called "k2" which points to your MovieClip, but the name property was left blank, so its automatic name is "instance3".

The reason for this seemingly convenient pointer is because by default Flash IDE has "Automatically declare stage instances" enabled. Seeing that you've created library objects, a property pointing to your MovieClip has automatically been created in root.

This isn't an option if you've manually created your objects at runtime. Normally, you would need to manually declare these to use dot.notation syntax.

k2.name = "k2";
root.addChild(k2);
root[k2.name] = k2;

Conversely, you could use root.getChildByName("k2") and forego the pointer creation in the root object. In many cases, this would be the correct way of doing it, although a bit more cumbersome.

k2 demo_tekst after: podmieniony tekst

If you come from Flash IDE and AS2, you're probably used to creating ActionScript directly on the timeline of each subordinate object. Don't do that in AS3.

It is my belief that the demo_tekst variable is not initialized because the MovieClip is not played, ergo there is no k2.demo_tekst until you've dynamically created it outside of your MovieClip object by writing k2.demo_tekst = 'podmieniony tekst'; Because MovieClips are dynamic, you can spawn these variables without conflict (not so with non-dynamic objects like Sprite or Shape).

Consider creating your MovieClips completely dynamically as follows:

var k1:MovieClip = new MovieClip();
k1.name = "kloc1";
k1.demo_text = "replacement text";
addChild(k1);
trace(k1.name + ".demo_text = " + k1.demo_text);
// outputs:  kloc1.demo_text = replacement text

k2 name from k1 obj: instance3

oryginalny tekst

The first line is expected (since you never named the k2 object), but this is where order of operation becomes interesting in timeline code (highly recommend not doing it). After the movieclip is parented to the MainTimeline, the code inside the timeline of your child MovieClip is finally run, which then overwrites the internal property demo_tekst.

I hope this clarifies things. Again, I highly implore you to write all your code in one document if you want to keep things simple. You can do this on the first frame, or write it externally and include it in your timeline.

If you're ready to go beyond the basics, consider creating your own class objects and importing them. This gives you the power of creating complex properties and functions on your custom objects (which appears to be your original intent).