Add FromIterator implementations for Id

Author: madsmtm

crates/objc2/CHANGELOG.md

@@ -54,6 +54,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   `extern_protocol!` and `declare_class!`.
 * Added `rc::IdIntoIterator` helper trait and forwarding `IntoIterator`
   implementations for `rc::Id`.
+* Added `rc::IdFromIterator` helper trait for implementing `IntoIterator`
+  for `rc::Id`.
 
 ### Changed
 * **BREAKING**: `objc2::rc::AutoreleasePool` is now a zero-sized `Copy` type

crates/objc2/src/rc/id.rs

@@ -56,13 +56,15 @@ use crate::{ffi, ClassType, Message};
 /// live on the stack, but instead must reside on the heap).
 ///
 /// Note that because of current limitations in the Rust trait system, some
-/// traits like [`Default`] and [`IntoIterator`] are not directly
-/// implementable on `NSString`; for that ues-case, we provide the
-/// [`DefaultId`] and [`IdIntoIterator`] traits, which make the aforementioned
-/// traits available on `Id`.
+/// traits like [`Default`], [`IntoIterator`], [`FromIterator`], [`From`] and
+/// [`Into`] are not directly implementable on `NSString`; for that use-case,
+/// we instead provide the [`DefaultId`], [`IdIntoIterator`] and
+/// [`IdFromIterator`] traits, which make some of the the aforementioned
+/// traits implementable on `Id`.
 ///
-/// [`IdIntoIterator`]: crate::rc::IdIntoIterator
 /// [`DefaultId`]: crate::rc::DefaultId
+/// [`IdIntoIterator`]: crate::rc::IdIntoIterator
+/// [`IdFromIterator`]: crate::rc::IdFromIterator
 ///
 ///
 /// # Memory layout

crates/objc2/src/rc/id_traits.rs

@@ -23,7 +23,7 @@ impl<T: ?Sized + DefaultId> Default for Id<T> {
 /// Helper trait to implement [`IntoIterator`] on [`Id`].
 ///
 /// This should be implemented in exactly the same fashion as if you were
-/// implementing `IntoIterator` for your type normally.
+/// just implementing `IntoIterator` for your type normally.
 //
 // Note that [`Box<T>` gets to cheat with regards moves][box-move], so
 // `boxed.into_iter()` is possible, while `id.into_iter()` is not possible
@@ -108,6 +108,23 @@ where
     }
 }
 
+/// Helper trait to implement [`FromIterator`] on [`Id`].
+///
+/// This should be implemented in exactly the same fashion as if you were
+/// just implementing `FromIterator` for your type normally.
+pub trait IdFromIterator<T>: Sized {
+    /// Creates an `Id` from an iterator.
+    fn id_from_iter<I>(iter: I) -> Id<Self>
+    where
+        I: IntoIterator<Item = T>;
+}
+
+impl<T, U: IdFromIterator<T>> FromIterator<T> for Id<U> {
+    #[inline]
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
+        U::id_from_iter(iter)
+    }
+}
 
 #[cfg(test)]
 mod tests {
@@ -179,12 +196,18 @@ mod tests {
         }
     }
 
-    impl<'a> IntoIterator for Id<Collection> {
+    impl IdIntoIterator for Collection {
         type Item = Id<NSObject>;
         type IntoIter = IntoIter;
 
-        fn into_iter(self) -> Self::IntoIter {
-            IntoIter(self)
+        fn id_into_iter(this: Id<Self>) -> Self::IntoIter {
+            IntoIter(this)
+        }
+    }
+
+    impl IdFromIterator<Id<NSObject>> for Collection {
+        fn id_from_iter<I: IntoIterator<Item = Id<NSObject>>>(_iter: I) -> Id<Self> {
+            Collection::default_id()
         }
     }
 
@@ -207,4 +230,10 @@ mod tests {
 
         for _ in obj {}
     }
+
+
+    #[test]
+    fn test_from_iter() {
+        let _: Id<Collection> = [NSObject::new()].into_iter().collect();
+    }
 }

crates/objc2/src/rc/mod.rs

@@ -62,6 +62,6 @@ pub use self::autorelease::{
     autoreleasepool, autoreleasepool_leaking, AutoreleasePool, AutoreleaseSafe,
 };
 pub use self::id::Id;
-pub use self::id_traits::{DefaultId, IdIntoIterator};
+pub use self::id_traits::{DefaultId, IdIntoIterator, IdFromIterator};
 pub use self::test_object::{__RcTestObject, __ThreadTestData};
 pub use self::weak_id::WeakId;