Document the UserData trait
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src/lua.rs
76
src/lua.rs
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@ -1081,6 +1081,82 @@ impl<'lua, T: UserData> UserDataMethods<'lua, T> {
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}
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/// Trait for custom userdata types.
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///
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/// By implementing this trait, a struct becomes eligible for use inside Lua code. Implementations
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/// of `ToLua` and `FromLua` are automatically provided.
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///
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/// # Examples
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///
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/// ```
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/// # extern crate rlua;
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/// # use rlua::{Lua, UserData, Result};
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/// # fn try_main() -> Result<()> {
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/// struct MyUserData(i32);
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///
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/// impl UserData for MyUserData {}
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///
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/// let lua = Lua::new();
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///
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/// // `MyUserData` now implements `ToLua`:
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/// lua.globals().set("myobject", MyUserData(123))?;
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///
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/// lua.exec::<()>("assert(type(myobject) == 'userdata')", None)?;
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/// # Ok(())
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/// # }
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/// # fn main() {
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/// # try_main().unwrap();
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/// # }
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/// ```
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///
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/// Custom methods and operators can be provided by implementing `add_methods` (refer to
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/// [`UserDataMethods`] for more information):
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///
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/// ```
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/// # #[macro_use] extern crate hlist_macro;
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/// # extern crate rlua;
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/// # use rlua::{Lua, MetaMethod, UserData, UserDataMethods, Integer, Result};
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/// # fn try_main() -> Result<()> {
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/// struct MyUserData(i32);
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///
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/// impl UserData for MyUserData {
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/// fn add_methods(methods: &mut UserDataMethods<Self>) {
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/// methods.add_method("get", |lua, this, args| {
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/// # let _ = (lua, args); // used
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/// lua.pack(this.0)
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/// });
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///
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/// methods.add_method_mut("add", |lua, this, args| {
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/// let hlist_pat![value]: HList![Integer] = lua.unpack(args)?;
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///
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/// this.0 += value as i32;
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/// lua.pack(())
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/// });
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///
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/// methods.add_meta_method(MetaMethod::Add, |lua, this, args| {
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/// let hlist_pat![value]: HList![Integer] = lua.unpack(args)?;
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/// lua.pack(this.0 + value as i32)
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/// });
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/// }
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/// }
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///
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/// let lua = Lua::new();
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///
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/// lua.globals().set("myobject", MyUserData(123))?;
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///
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/// lua.exec::<()>(r#"
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/// assert(myobject:get() == 123)
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/// myobject:add(7)
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/// assert(myobject:get() == 130)
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/// assert(myobject + 10 == 140)
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/// "#, None)?;
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/// # Ok(())
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/// # }
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/// # fn main() {
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/// # try_main().unwrap();
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/// # }
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/// ```
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///
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/// [`UserDataMethods`]: struct.UserDataMethods.html
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pub trait UserData: 'static + Sized {
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/// Adds custom methods and operators specific to this userdata.
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fn add_methods(_methods: &mut UserDataMethods<Self>) {}
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