From b6937fd21d9142381466bdd48bfd7712a1567afd Mon Sep 17 00:00:00 2001
From: Tristan Guichaoua <tguichaoua.dev@gmail.com>
Date: Mon, 8 Aug 2022 14:43:06 +0200
Subject: [PATCH] add RhaiCustomType trait and build_type method

---
 src/api/build_type.rs | 67 +++++++++++++++++++++++++++++++++++++++++++
 src/api/mod.rs        |  2 ++
 src/lib.rs            |  2 +-
 3 files changed, 70 insertions(+), 1 deletion(-)
 create mode 100644 src/api/build_type.rs

diff --git a/src/api/build_type.rs b/src/api/build_type.rs
new file mode 100644
index 00000000..785034e1
--- /dev/null
+++ b/src/api/build_type.rs
@@ -0,0 +1,67 @@
+use crate::Engine;
+
+/// Trait to build a custom type for use with the [`Engine`].
+/// i.e. register the type, getters, setters, methods, etc...
+///
+/// # Example
+///
+/// ```
+/// use rhai::{Engine, RhaiCustomType};
+///
+/// #[derive(Debug, Clone, Eq, PartialEq)]
+/// struct TestStruct {
+///     field: i64
+/// }
+///
+/// impl TestStruct {
+///     fn new() -> Self {
+///         Self { field: 1 }
+///     }
+///     fn update(&mut self, offset: i64) {
+///         self.field += offset;
+///     }
+/// }
+///
+/// impl RhaiCustomType for TestStruct {
+///     fn build(engine: &mut Engine) {
+///         engine
+///             .register_type::<Self>()
+///             .register_fn("new_ts", Self::new)
+///             .register_fn("update", Self::update);
+///     }
+/// }
+///
+/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
+///
+/// let mut engine = Engine::new();
+///
+/// // Register API for the custom type.
+/// engine.build_type::<TestStruct>();
+///
+/// # #[cfg(not(feature = "no_object"))]
+/// assert_eq!(
+///     engine.eval::<TestStruct>("let x = new_ts(); x.update(41); x")?,
+///     TestStruct { field: 42 }
+/// );
+/// # Ok(())
+/// # }
+/// ```
+pub trait RhaiCustomType {
+    /// Builds the custom type for use with the [`Engine`].
+    /// i.e. register the type, getters, setters, methods, etc...
+    fn build(engine: &mut Engine);
+}
+
+impl Engine {
+    /// Build a custom type for use with the [`Engine`].
+    /// i.e. register the type, getters, setters, methods, etc...
+    ///
+    /// See [`RhaiCustomType`].
+    pub fn build_type<T>(&mut self) -> &mut Self
+    where
+        T: RhaiCustomType,
+    {
+        T::build(self);
+        self
+    }
+}
diff --git a/src/api/mod.rs b/src/api/mod.rs
index f24777c6..635082dd 100644
--- a/src/api/mod.rs
+++ b/src/api/mod.rs
@@ -28,6 +28,8 @@ pub mod custom_syntax;
 
 pub mod deprecated;
 
+pub mod build_type;
+
 #[cfg(feature = "metadata")]
 pub mod definitions;
 
diff --git a/src/lib.rs b/src/lib.rs
index 9ad7317f..0a19d5fc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -166,7 +166,7 @@ type ExclusiveRange = std::ops::Range<INT>;
 /// An inclusive integer range.
 type InclusiveRange = std::ops::RangeInclusive<INT>;
 
-pub use api::events::VarDefInfo;
+pub use api::{build_type::RhaiCustomType, events::VarDefInfo};
 pub use ast::{FnAccess, AST};
 pub use engine::{Engine, OP_CONTAINS, OP_EQUALS};
 pub use eval::EvalContext;