Attribute Macro mlua_gen

#[mlua_gen]

mlua_gen

Allow quick modifications of Rust’s struct and enum in Lua with mlua

Struct

Example

The following rust code

use mlua_gen::mlua_gen;

#[mlua_gen(impl = [default(), age(&self), set_age(&mut self, u8)])]
#[derive(Default)]
pub(crate) struct Human {
    pub(crate) name: String,
    age: u8,
}

impl Human {
    pub(crate) fn age(&self) -> String {
        format!("{} years old", self.age)
    }
    pub(crate) fn set_age(&mut self, age: u8) {
        self.age = age;
    }
}

Can be used in lua easily like this

local human = Human.default()
human:set_age(42)
human.name = "Martin"
assert(human.name == "Martin")
assert(human:age() == "42 years old")

Attributes

get

Value: pub | pub(crate) | pub(super) | * | [Ident]

Define which attributes should have getters values. (By default pub(super))

• pub(super) includes pub and pub(crate)
• pub(crate) includes pub
• * represents all fields
• [Ident] which fields should have getter ?

Example

#[mlua_gen(get = [a, c])]
struct MyFields {
    a: usize,
    pub(super) b: usize,
    pub(crate) c: usize,
    pub d: usize,
}

Lua:

print(fields.a)
print(fields.b) -- nil
print(fields.c)
print(fields.d) -- nil

set

Value: pub | pub(crate) | pub(super) | * | [Ident]

See get for more information about visibility

Define which attributes should have setters values. (By default pub(super))

Example

#[mlua_gen(set = [a, c])]
struct MyFields {
    a: usize,
    pub(super) b: usize,
    pub(crate) c: usize,
    pub d: usize,
}

Lua:

fields.a = 42
-- fields.b cannot be set
fields.c = 42
-- fields.d cannot be set

impl

Value: [ExprCall] (ExprCall being a function call expression: invoke(a, b))

The functions that are implemented for this struct and that you want to be usable in Lua

Example

#[mlua_gen(impl = [default(), age(&self), set_age(&mut self, u8)])]
#[derive(Default)]
pub(crate) struct Human {
    pub(crate) name: String,
    age: u8,
}

impl Human {
    pub(crate) fn age(&self) -> String {
        format!("{} years old", self.age)
    }
    pub(crate) fn set_age(&mut self, age: u8) {
        self.age = age;
    }
}

Lua:

local human = Human.default()
human:set_age(42)
print(human:age()) -- 42

custom_field

Value: Ident

The Ident should be the ident of a function that has for signature fn(&mut ::mlua::UserDataFields<Self>) -> ();

Posibility to add custom fields that will be usable in lua.

Example

#[mlua_gen(custom_fields = fields)]
struct Human {
    pub name: String,
    pub age: u8,
}
fn fields<T: ::mlua::UserDataFields<Human>>(fields: &mut T) {
    fields.add_field_method_get("name_age", |_, this| {
        Ok(format!("{} ({})", this.name, this.age))
    });
}

Lua:

human.age = 42
human.name = "Martin"
assert(human.name_age == "Martin (42)")

custom_impls

Value: Ident

Same as custom_field but with UserDataMethods

Enum

Example

The following rust code

use mlua_gen::mlua_gen;

#[mlua_gen(impl = [default(), name(&self)])]
#[derive(Default)]
enum Animal {
    #[default]
    Pig,
    Dog(String),
    Cat { name: String, age: u8 },
}

impl Animal {
    pub(crate) fn name(&self) -> String {
        match self {
            Animal::Pig => "Piggy".to_owned(),
            Animal::Dog(name) => name.to_owned(),
            Animal::Cat { name, .. } => name.to_owned(),
        }
    }
}

Can be used easily with the following lua code

local pig = Animal.Pig -- or in our case, Animal:default()
local dog = Animal.Dog ( "Doggo" )
local cat = Animal.Cat { name = "Neko", age = 8 }

-- method call
assert(pig:name() == "Piggy")
assert(dog:name() == "Doggo")
assert(cat:name() == "Neko")

-- access with field
--- Pig
assert(pig.pig)
assert(pig.dog == nil)
assert(pig.cat == nil)
--- Dog
assert(dog.pig == nil)
assert(dog.dog[1] == "Doggo")
assert(dog.cat == nil)
--- Cat
assert(cat.pig == nil)
assert(cat.dog == nil)
assert(cat.cat.name == "Neko")
assert(cat.cat.age == 8)