Add TryPartialEq trait to check for equality

Signed-off-by: trivernis <trivernis@protonmail.com>

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "multi-trait-object"
-version = "0.1.2"
+version = "0.1.3"
 edition = "2021"
 readme = "README.md"
 license = "Apache-2.0"

src/tests.rs

@@ -26,7 +26,7 @@ impl ChangeStruct for TestStruct {
     }
 }
 
-impl_trait_object!(TestStruct, dyn RawClone, dyn ChangeStruct, dyn Debug);
+impl_trait_object!(TestStruct, dyn RawClone, dyn PartialEqAny, dyn ChangeStruct, dyn Debug);
 
 #[test]
 fn it_creates_fat_pointers() {
@@ -95,3 +95,12 @@ fn it_returns_type_information() {
     assert!(mto.implements::<dyn Debug>());
     assert!(mto.implements::<dyn ChangeStruct>());
 }
+
+#[test]
+fn it_tries_partial_eq() {
+    let mto = TestStruct::default().into_multitrait();
+    let mto_eq = TestStruct::default().into_multitrait();
+    let mto_neq = TestStruct {test: String::from("no"), a: 6}.into_multitrait();
+    assert!(mto.try_eq(&mto_eq).unwrap());
+    assert_eq!(mto.try_eq(&mto_neq).unwrap(), false);
+}

src/trait_impl/mod.rs

@@ -1,5 +1,7 @@
 mod try_clone;
 mod debug;
+mod try_partial_eq;
 
 pub use try_clone::*;
 pub use debug::*;
+pub use try_partial_eq::*;

src/trait_impl/try_clone.rs

@@ -15,14 +15,15 @@ pub unsafe trait RawClone {
     unsafe fn raw_clone(&self) -> *mut ();
 }
 
+/// A trait that tries cloning an object and returns an option
+/// with the variant depending on the result. For a multitrait object
+/// to be clonable it needs to have the [RawClone] trait registered.
 unsafe impl<T: Clone> RawClone for T {
     unsafe fn raw_clone(&self) -> *mut () {
         Box::into_raw(Box::new(self.clone())) as *mut ()
     }
 }
 
-/// A trait that tries cloning an object and returns an option
-/// with the variant depending on the result.
 impl TryClone for MultitraitObject {
     fn try_clone(&self) -> Option<Self> {
         let clone = self.downcast_trait::<dyn RawClone>()?;

src/trait_impl/try_partial_eq.rs

@@ -0,0 +1,37 @@
+use std::any::{Any};
+use crate::MultitraitObject;
+
+/// Compares the given value with an Any trait object.
+/// Register this trait if you want to compare two Multitrait objects
+/// with the [TryPartialEq] trait.
+pub trait PartialEqAny {
+    fn partial_equal_any(&self, other: &dyn Any) -> bool;
+}
+
+impl<T: PartialEq + Any> PartialEqAny for T {
+    fn partial_equal_any(&self, other: &dyn Any) -> bool {
+        if let Some(other) = other.downcast_ref::<T>() {
+            self.eq(other)
+        } else {
+            false
+        }
+    }
+}
+
+/// Tries to compare the MultitraitObject with another object
+/// and returns Some(bool) when the underlying type implements PartialEq and
+/// has the [PartialEqAny] trait registered on the object.
+pub trait TryPartialEq {
+    fn try_eq(&self, other: &Self) -> Option<bool>;
+}
+
+impl TryPartialEq for MultitraitObject {
+    fn try_eq(&self, other: &Self) -> Option<bool> {
+        if let Some(eq_any) = self.downcast_trait::<dyn PartialEqAny>() {
+            let any = other.downcast_trait::<dyn Any>().unwrap();
+            Some(eq_any.partial_equal_any(any))
+        } else {
+            None
+        }
+    }
+}