Saving games

Introduction

Save games can be complicated. For example, it may be desirable to store information from multiple objects across multiple levels. Advanced save game systems should allow for additional information about an arbitrary number of objects. This will allow the save function to scale as the game grows more complex.

Note

If you're looking to save user configuration, you can use the ConfigFile class for this purpose.

See also

You can see how saving and loading works in action using the Saving and Loading (Serialization) demo project.

Identify persistent objects

Firstly, we should identify what objects we want to keep between game sessions and what information we want to keep from those objects. For this tutorial, we will use groups to mark and handle objects to be saved, but other methods are certainly possible.

We will start by adding objects we wish to save to the "Persist" group. We can do this through either the GUI or script. Let's add the relevant nodes using the GUI:

../../_images/groups.png

Once this is done, when we need to save the game, we can get all objects to save them and then tell them all to save with this script:

var save_nodes = get_tree().get_nodes_in_group("Persist")
for i in save_nodes:
    # Now, we can call our save function on each node.

Serializing

The next step is to serialize the data. This makes it much easier to read from and store to disk. In this case, we're assuming each member of group Persist is an instanced node and thus has a path. GDScript has helper class JSON to convert between dictionary and string, Our node needs to contain a save function that returns this data. The save function will look like this:

func save():
    var save_dict = {
        "filename" : get_scene_file_path(),
        "parent" : get_parent().get_path(),
        "pos_x" : position.x, # Vector2 is not supported by JSON
        "pos_y" : position.y,
        "attack" : attack,
        "defense" : defense,
        "current_health" : current_health,
        "max_health" : max_health,
        "damage" : damage,
        "regen" : regen,
        "experience" : experience,
        "tnl" : tnl,
        "level" : level,
        "attack_growth" : attack_growth,
        "defense_growth" : defense_growth,
        "health_growth" : health_growth,
        "is_alive" : is_alive,
        "last_attack" : last_attack
    }
    return save_dict

This gives us a dictionary with the style { "variable_name":value_of_variable }, which will be useful when loading.

Saving and reading data

As covered in the File system tutorial, we'll need to open a file so we can write to it or read from it. Now that we have a way to call our groups and get their relevant data, let's use the class JSON to convert it into an easily stored string and store them in a file. Doing it this way ensures that each line is its own object, so we have an easy way to pull the data out of the file as well.