SpecialKeys

SpecialKeys allow you to declaratively configure a Body at creation time by adding new data. They are especially helpful when creating custom engine features such as Tags.

How do they work?

SpecialKeys work by using a table as a unique key in the body creation table. This naturally means that there cannot be SpecialKey duplicates because you cannot have a key equal 2 values.

Comet By default includes 2 default special keys.

Name

You can use the Name special key to give a name identifier to an object:

local player = Universe:Body {
    [Comet.Name] = "Player"
}

Children

You can use the Children special key to parent a list of Bodies to the body being created.

local player = Universe:Body {
    [Comet.Children] = {
        Universe:Body {}
    }
}

Defining your own SpecialKeys

The real power of special keys comes when you define your own. You can define one like this:

local TestKey = {
    Type = "SpecialKey",
    Stage = "PreComponents",
    Name = "TestKey",
    Method = function(body, value)
        print(value)
    end,
}

The Stage field defines what Stage the Key will run at, there are 3 stages:

• PreComponents - Runs before any components are created. Use for structural setup.
• InitComponents - Runs after all components exist and their Init() methods have run.
• PostComponents - Runs after the body is fully constructed and ready for use.

To learn more about defining special keys, check out the tag project.