Constructing Arbitrary Types

When interfacing with bevy, we do this via reflection. While the generated bindings do not cover constructors for every single type that bevy or other libraries provide, reflection allows us to construct some (not all types implement FromReflect) types from dynamic structs.

BMS exposes this ability to all script writers via the construct global function.

Structs

The following struct:

pub struct MyStruct {
    pub my_field: String
}

can be constructed from lua like so:

local MyStruct = world.get_type_by_name("MyStruct")
local concrete_my_struct = construct(MyStruct, {
    my_field = "hello"
})

Tuple Structs

The following tuple struct:

pub struct MyTupleStruct(pub String);

can be constructed like so:

local MyTupleStruct = world.get_type_by_name("MyTupleStruct")
local concrete_my_tuple_struct = construct(MyTupleStruct, {
    _1 = "hello"
})

Enums

The following enum:

pub enum MyEnum {
    VariantA {
        field: String
    },
    VariantB
}

can be constructed like so:

local MyEnum = world.get_type_by_name("MyEnum")
local variantA = construct(MyEnum, {
    variant = "VariantA",
    field = "hello"
})
local variantB = construct(MyEnum, {
    variant = "VariantB"
})

When working with enums you can also figure out the variant at runtime using variant_name:

if my_enum:variant_name() == "VariantA" then
    print(my_enum.field)
end