LethalModDataLib

A library for mod data saving & loading.

What is this?

This library provides a standardised way to save and load persistent data for mods. It is designed to be easy to use and flexible, offering multiple different ways to interact with the system, depending on your needs.

Data is saved in .moddata files, which are stored in the same location as the vanilla save files. Instead of having a single file, or a file per mod, the library has a file for each save file, and a file for general data - essentially mimicking the vanilla save system. This ensures that mods do not pollute the vanilla save files. The library makes use of ES3 to handle the actual saving and loading of the data, which should be compatible with most Unity types.

When saving and loading data through the library, keys are automatically generated based on your mod's GUID and assembly information (depending on the approach used - see below). This ensures that your data does not conflict with other mods' data, and that it is easy to find and debug.

File structure

ZeekerssRBLX
    └── Lethal Company
        ├── LCGeneralSaveData
        ├── LCGeneralSaveData.moddata
        ├── LCSaveFile1
        ├── LCSaveFile1.moddata
        ├── LCSaveFile2
        ├── LCSaveFile2.moddata
        ├── LCSaveFile3
        └── LCSaveFile3.moddata

As you can see, there is a .moddata file for each vanilla save file, including the general save file. Mods do not have individual .moddata files, and do not touch the vanilla save files.

Supported types

See Easy Save 3's documentation for a list of supported types. In general, most Unity types are supported, as well as custom classes and structs that are serializable.

Usage

There are 3 ways to use this library. They can all be used in the same project, with some caveats.

1. Using the ModData attribute

This is the easiest and most automated way to use the library. Unless you need to manually handle saving and loading, this is the way to go. Note that this method still allows you to manually handle saving and/or loading if you need to, so you are not limited to the automated part.

Depending on the attribute configuration, the library will take care of saving and loading data for you, in a way that is seamless and "invisible" / does not require you to add any additional code beyond the attribute.

The ModData attribute can be used to mark fields & properties that should be saved and loaded through the handler's event hooks. When applied to static fields or properties, the attribute will automatically register the class with the ModDataHandler, and the data will be saved and loaded depending on the attribute's parameters. When applied to non-static fields or properties, the attribute will be ignored unless you register the class' instance with the ModDataHandler through the RegisterInstance method.

The ModData handler will save the original value of your field or property, and use this when no mod data exists when loading a save file. This ensures you don't need to manually reset a value whenever a player would switch saves, or when a new save is created. If you wish to reset a value when a game over happens, you can use the ResetWhen parameter.

This is the attribute's constructor signature:

public ModDataAttribute(SaveWhen saveWhen, LoadWhen loadWhen, SaveLocation saveLocation, string? baseKey = null)

These are options for its 4 parameters:

• SaveWhen (enum) - When the data should be saved
  • Manual - Manually handled by you, the modder
  • OnAutoSave - When the game is autosaved (= Whenever the ship returns to orbit)
  • OnSave - When the game is saved (Most frequent - also called by autosaves)
• LoadWhen (enum) - When the data should be loaded
  • Manual - Manually handled by you, the modder
  • OnLoad - When a save file is loaded, right after all vanilla loading is done
  • OnRegister - When the attribute is registered, as soon as possible
• SaveLocation (enum) - Where the data should be saved
  • GeneralSave - In a .moddata file that fulfills the same purpose as vanilla's LCGeneralSaveData file
  • CurrentSave - In a .moddata file that is specific to the current save file
• ResetWhen (enum) - When the data should be reset
  • Manual - Manually handled by you, the modder
  • OnGameOver - When a game over happens (quota not reached, ship reset)
• BaseKey - Strongly recommended to leave default unless you know what you're doing - The base key for the data. This is used to create the key for the field in the .moddata file. If not set, the library will sort this out. In general, you should not need to set this unless you are e.g. trying to access the data from another mod which is not enabled. Note that using the same base key for multiple fields will very likely cause unexpected behaviour. (If you do want to use the same key as a currently enabled mod, for some case I can't imagine, you should be using the GetModDataKey method in ModDataHelper to fetch its information).

Important

To manually trigger saving & loading of an attribute-marked field or property, you can use the SaveLoadHandler class' SaveData and LoadData methods, using an IModDataKey object. This can be fetched using the GetModDataKey method in ModDataHelper.

The ModData attribute can be used on fields and properties, both static and instanced ones, as well as public, private and internal ones.

Tip

Remember that non-static (instanced) fields and properties with the ModData attribute will be ignored unless you register the class' instance with the ModDataHandler through the RegisterInstance method. De-registering an instance is done through the DeRegisterInstance method.

Tip

Example instanced usage:

public class SomeClass
{
    [ModData(SaveWhen.OnSave, LoadWhen.OnLoad, SaveLocation.GeneralSave)]
    private int __someInt;
    
    [ModData(SaveWhen.OnAutoSave, LoadWhen.OnLoad, SaveLocation.CurrentSave)]
    public string SomeString { get; set; } = "SomeDefaultValue";
    
    [ModData(SaveWhen.Manual, LoadWhen.OnLoad, SaveLocation.GeneralSave)]
    private float __someFloat;
    
    // Some method in which we manually handle __someFloat's saving, since its attribute is set to SaveWhen.Manual
    private void SomeMethod()
    {
        // (...)
        
        SaveLoadHandler.SaveData(ModDataHelper.GetModDataKey(this, nameof(__someFloat)));
        
        // Note that we can also force a save or load of automated fields/properties:
        SaveLoadHandler.LoadData(ModDataHelper.GetModDataKey(this, nameof(SomeString)));
        
        // This might be useful to instantiate values for instances that may be null when the OnLoad event is called.
        if (string.IsNullOrEmpty(SomeString))
        {
            // (...)
        }
        
        // (...)
    }
}

// In some other class
public class SomeOtherClass
{
    private SomeClass __someClass;
    
    public SomeOtherClass()
    {
        __someClass = new SomeClass();
        
        ModDataHandler.RegisterInstance(someClass, "someInstanceName"); // Register an instance of SomeClass with the ModDataHandler
    }
}

Tip

Example static usage:

public class SomeClass
{
    [ModData(SaveWhen.OnSave, LoadWhen.OnLoad, SaveLocation.GeneralSave)]
    private static int __someInt;
    
    [ModData(SaveWhen.Manual, LoadWhen.OnLoad, SaveLocation.CurrentSave)]
    public static string SomeString { get; set; } = "SomeDefaultValue";
    
    public void SomeMethod()
    {
        // (...)
        
        SaveLoadHandler.SaveData(ModDataHelper.GetModDataKey(typeof(this), nameof(SomeString))); // Note the use of typeof(this) instead of this
        
        // (...)
    }
}

public class SomeOtherClass
{
    // (...)
    
    public void SomeOtherMethod()
    {
        // (...)
        
        SaveLoadHandler.SaveData(ModDataHelper.GetModDataKey(typeof(SomeClass), nameof(SomeClass.SomeString))); // Note the use of typeof(SomeClass)
        
        // (...)
    }
    
    // (...)
}

Warning

When using the Manual parameter for saving and/or loading, you need to use the methods that take an IModDataKey as parameter. This is because the other save/load methods will result in a different key being used (unless you go through the unnecessary trouble of finding out the key yourself). Not doing this will cause your data to be saved and loaded in a different location, unless you're handling it manually entirely - in which case you don't need the attribute in the first place.

2. Using the ModDataContainer abstract class

This way of using the library requires you to set up a class that inherits from ModDataContainer. Any fields or properties in this class will be saved and loaded automatically, without the need for any attributes. You are essentially creating a "container" for your mod data.

The ModDataContainer class has a number of properties and methods that you can override to customize its behavior:

• Properties:
  • SaveLocation - Where the data should be saved. Defaults to SaveLocation.CurrentSave
  • OptionalPrefixSuffix - A string that will be appended to the prefix for keys of fields in the container. This is useful in case you want to have different instances of the same container in the same save file; for example a container per player. Defaults to string.Empty
• Methods:
  • GetPrefix - Strongly recommended to leave default unless you know what you're doing - Returns the prefix for keys of fields in the container. Defaults to the assembly name and the class name, separated by a dot. ( e.g. MyMod.MyContainer). If OptionalPrefixSuffix is set, it will be appended to the prefix like so: MyMod.MyContainer.MyOptionalPrefixSuffix
  • Save - Strongly recommended to leave default unless you know what you're doing - Saves the data in the container. Should be called by the modder when the data should be saved.
  • Load - Strongly recommended to leave default unless you know what you're doing - Loads the data in the container. Should be called by the modder when the data should be loaded.
  • Pre/PostSave/Load - Methods that are called before and after the saving and loading of the container's data. Can be used to perform additional operations, such as logging or data validation.

There is also an additional attribute that can be used to mark fields or properties as ignored by the container:

public ModDataIgnoreAttribute(IgnoreFlags ignoreFlags = IgnoreFlags.None)

The IgnoreFlags enum has the following options:

• None - No flags. Completely ignore the field or property.
• OnSave - Ignore the field or property when saving.
• OnLoad - Ignore the field or property when loading.
• IfNull - Ignore the field or property if it is null.
• IfDefault - Ignore the field or property if it is the default value for its type.

Tip

Example usage:

public class SomeContainer : ModDataContainer
{
    private int __someInt;
    public string SomeString { get; set; } = "SomeDefaultValue";
    [ModDataIgnore(IgnoreFlags.IfDefault)]
    private float __someFloat;
    private List<int> __someList;
    
    // Use the constructor to set the OptionalPrefixSuffix, so we can have multiple instances of this container without them overwriting each other
    public SomeContainer(string name)
    {
        OptionalPrefixSuffix = name;
    }
    
    // Override the PostLoad method to ensure that the list is not null
    protected override void PostLoad()
    {
        if (__someList == null)
        {
            __someList = new List<int>();
        }
    }
}

// In some other class
public class SomeClass
{
    private SomeContainer __container;
    
    public SomeClass()
    {
        __container = new SomeContainer("SomeName"); // Create a new instance of the container
        __container.Load(); // Load the container's data, if any exists
    }
    
    // Some method in which we manually handle saving the container's data
    private void SomeMethod()
    {
        // (...)
        
        __container.Save(); // Save the container's data
        
        // (...)
    }
}

Warning

Note: You should not use the ModData attribute on (static) fields or properties in a class that inherits from ModDataContainer. This will cause the fields to be saved/loaded twice, once by the container and once by the attribute. Additionally, the keys for the fields will be different, which can cause inconsistencies depending on when the data is saved and loaded. When used on non-static fields or properties, the attribute will be ignored unless you register the class' instance with the ModDataHandler, which is also not recommended for the same reasons.

3. Using the SaveLoadHandler save & load methods

This is the "good old" manual way of saving and loading data. You can use the SaveLoadHandler class' methods to manually handle saving and loading of data. This is useful if you need to save and load data in a way / at a time that is not covered by the other options, or if you want to build your own handler for saving and loading.

The SaveLoadHandler class has a SaveData & LoadData method, with two public signatures each:

// The recommended method to use for manual saving.
// It is recommended to leave autoAddGuid as true, since this will automatically add your mod's guid to the key; preventing conflicts with other mods.
public static bool SaveData<T>(T? data, string key, SaveLocation saveLocation = SaveLocation.CurrentSave, bool autoAddGuid = true)
    
// For usage with the SaveWhen.Manual attribute parameter. You will need to fetch the IModDataKey object for the field or property you want to save.
// This can be done using the GetModDataKey method in ModDataHelper.
// Note: This will save the data from the field/property, rather than requiring you to pass a value through the method.
public static bool SaveData(IModDataKey modDataKey)

// The recommended method to use for manual loading.
// It is recommended to leave autoAddGuid as true, since this will automatically add your mod's guid to the key; preventing conflicts with other mods.
public static T? LoadData<T>(string key, T? defaultValue = default, SaveLocation saveLocation = SaveLocation.CurrentSave, bool autoAddGuid = true)
    
// For usage with the LoadWhen.Manual attribute parameter. You will need to fetch the IModDataKey object for the field or property you want to load.
// This can be done using the GetModDataKey method in ModDataHelper.
// Note: This will load the data into the field/property, rather than requiring you to assign the value returned by the method.
public static bool LoadData(IModDataKey modDataKey)

Tip

Example usage:

public class SomeClass
{
    private int __someInt;
    private string SomeString { get; set; };
    
    [ModData(SaveWhen.Manual, LoadWhen.Manual, SaveLocation.GeneralSave)]
    private float __someFloat;
    
    // Some method in which we manually handle saving __someInt
    private void SomeMethod()
    {
        // (...)
        
        SaveLoadHandler.SaveData(__someInt, "SomeIntKey");
        
        // (...)
    }
    
    // Some method in which we manually handle loading __someString
    private void SomeOtherMethod()
    {
        // (...)
        
        SomeString = SaveLoadHandler.LoadData<string>("SomeStringKey", "SomeDefaultValue");
        
        // (...)
    }
    
    // Some method in which we manually handle saving __someFloat
    private void YetAnotherMethod()
    {
        // (...)
        
        SaveLoadHandler.SaveData(ModDataHelper.GetModDataKey(this, nameof(__someFloat)));
        
        // (...)
    }
    
    // Some method in which we manually handle loading __someFloat
    private void AndAnotherMethod()
    {
        // (...)
        
        SaveLoadHandler.LoadData(ModDataHelper.GetModDataKey(this, nameof(__someFloat)));
        
        // (...)
    }
}

Tips

• The library automatically removes the paired .moddata file when a save is deleted, so handle this accordingly in your mod. (e.g. by hooking into the PostDeleteFileEvent event from LethalEventsLib)
• Validate your data after loading, if you expect it to be in a certain state. If a value is missing when it is loaded, it will be set to the type's default value (0, null, etc...). This can be done in e.g. the PostLoad method of a ModDataContainer or in the method that loads the data. For attribute-based saving and loading, it is recommended to use properties, and to validate the value in the property's setter.
• Lethal Company sets its current save file to the last selected/loaded save file on game start. Keep this in mind if you are using the SaveLocation.CurrentSave parameter, and are manually handling saving and/or loading. This is not a concern if you are using the attribute without manual handling, if you are using the SaveLocation.GeneralSave parameter, or if you are saving/loading after a save file has been loaded.

Attribution

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