The onInit method

It is usual to need some initialization to be done to an struct's static members during map initialization, you can use an static onInit method to make code execute during map initialization.

Notice struct initializations are executed before any library initializer, if you require a library initializer to be executed before your initialization, use a library initializer instead. The relative order between different struct initializers depends on the location they are found in the map script, therefore they actually depend on things like libraries as well (A struct initializer inside a library will run before the initializers inside other libraries that require it and also before initializers inside scopes).