Tile-based movement using composition

darida12321

Here is the project-pitch: I want to create a sokoban-style box pushing game. That means that the player moves on a grid, and so do the boxes (maybe some other entities too). I figured the best way to do this is to create a TileBasedMovement component. The code is pretty much this:

This has two exported variables: an object to move, and a tilemap to get the tile size (and collisions, etc.).

The object to move is easy to set up. The player scene looks like this:

The Player node can be sent to the object field.

Here is the problem: I have no idea how to set the exported "tilemap" value to the actual tilemap. The actual level scene looks something like this:

However, there is no way to modify the player's TileBasedMovement component from here. Is there an option I can turn on to edit it which I haven't heard about before?

Some things I have tried before:
1) Setting up the tilemap with a Unique Name still does not make it assignable with the player scene
2) Setting up the player with an exported variable, then using setters to modify the tilemap's variable does not work. At the point of the exported value being set for the player, the component does not exist yet.
3) Similar to the second solution, I could mark the player script with the "tool" macro. This way I could set it such that whenever I edit the player's tilemap value in the editor, it also edits the component's tilemap value. However, this seems like a bit of an overkill for what I'm trying to achieve, and I'd have to add a bunch of extra code in the player script to make sure it's not being run inside the editor.
4) Probably the easiest thing would be to have the component's move function take in a tilemap as an argument instead of exporting it. Then the player can call it with its own exported tilemap value. This means that this value gets passed around quite a lot, which leads to extra code.

I think the ideal solution would be something like number 3, but it really does seem like an overkill for this situation. Is there any other approach I haven't heard about?

Edit: some new things I've learned:
5) There is an editable children option in the editor for instanciated scene, which solves the current problem pretty neatly, but there are a few cases that are still not covered.

If the player scene had multiple components (TileBasedMovement, TileBasedPathfinding, TileModifyer, etc...) then I'd have to set each of these individually to the same tileMap node, which is a lot of work. It seems like the tool macro might be the best solution here (but I'm still looking for any other approaches)
If I have 10 or 20 boxes in the game scene (all needing a tilemap), it's very bothersome to set it one-by-one. Is there something like a global value or a custom resource that I can create, set the boxes' tilemap to be that resource and then change what that resource actually means within a script?

xyz

darida12321 Assign it at runtime from a script attached to Game node. And as a general advice - don't overthink stuff like this.

darida12321

xyz I don't think that's reliable, since both the Player's position in the game tree, and the component's position in the player scene might change. (Or is there a way of tracking that reliably?)

But this is more of a thought experiment. I just started out with godot, and want to learn some more features. 2 of those solutions do work, they just aren't exactly what I want them to be. (just found out about the editable children properties too, which is very useful)

xyz

darida12321 Well if you want to get academic then the architecture should be set up in a way that player doesn't need to hold a reference to the tile map at all. A game logic script in a node that's hierarchically above both nodes should be handling it.

If you nevertheless insist on having it, then provide a method in the player class to set this reference at runtime. Nothing unreliable about that.

If you want to have it done from the editor, export the property in the top node of the player scene which will be accessible in the main scene and then re-assign that to the component at runtime startup, i.e. from the _ready() callback in the player's script.

darida12321

xyz Thanks for the advice, it really seems like simply passing the value down is the best (and most godot-like) way of doing this.

There is just one more approach I've been looking into, but idk if that's a wacky way of doing this or not. The current approach (game manager) would have to be updated every time a new item is introduced (box variants also need to get a tilemap individually). This is not a lot of code (mostly just one extra line per object), but still something that should be avoided.

I have been looking into how to create a resource from script files. Is it a common pattern to have a resource which contains a "tilemap" variable, then objects (player, box) can hook their components up to that resource, and have the game controller modify that at the ready function?

xyz

darida12321 You can try and see how it works.

As a general hint, Don't try to force ECS type of thinking when designing a system. Although you can "emulate" some aspects of ECS with nodes, Godot's forte is classic OOP. So if you're tempted to make something into a pseudo-ECS thingy, always ask yourself could it be handled more gracefully using good old OO.