From 35024e983a7397e2548739c9cfdd3f91cfd0e932 Mon Sep 17 00:00:00 2001
From: Red Davis <me@red.to>
Date: Fri, 15 Jul 2022 06:01:01 +0100
Subject: [PATCH] feat: add last() to async sequence (#36)

---
 .../Extensions/AsyncSequence+Extension.swift     | 10 ++++++++++
 .../Tests/Extensions/AsyncSequenceTests.swift    | 11 +++++++++--
 README.md                                        | 16 ++++++++++++++++
 3 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/Asynchrone/Source/Extensions/AsyncSequence+Extension.swift b/Asynchrone/Source/Extensions/AsyncSequence+Extension.swift
index 0d40e57..ede5558 100644
--- a/Asynchrone/Source/Extensions/AsyncSequence+Extension.swift
+++ b/Asynchrone/Source/Extensions/AsyncSequence+Extension.swift
@@ -50,6 +50,16 @@ extension AsyncSequence {
         }
     }
     
+    /// The last element of the sequence, if there is one.
+    public func last() async rethrows -> Element? {
+        var latestElement: Element?
+        for try await element in self {
+            latestElement = element
+        }
+        
+        return latestElement
+    }
+    
     /// Collect elements from a sequence.
     ///
     /// ```swift
diff --git a/AsynchroneTests/Tests/Extensions/AsyncSequenceTests.swift b/AsynchroneTests/Tests/Extensions/AsyncSequenceTests.swift
index 4e9e261..6e09a8e 100644
--- a/AsynchroneTests/Tests/Extensions/AsyncSequenceTests.swift
+++ b/AsynchroneTests/Tests/Extensions/AsyncSequenceTests.swift
@@ -28,8 +28,15 @@ final class AsyncSequenceTests: XCTestCase {
     // MARK: First
     
     func testFirst() async {
-        let firstValue = await self.sequence.first()
-        XCTAssertEqual(firstValue, 1)
+        let element = await self.sequence.first()
+        XCTAssertEqual(element, 1)
+    }
+    
+    // MARK: Last
+    
+    func testLast() async {
+        let element = await self.sequence.last()
+        XCTAssertEqual(element, 3)
     }
     
     // MARK: Collect
diff --git a/README.md b/README.md
index 8d7ca14..8523e9d 100644
--- a/README.md
+++ b/README.md
@@ -71,6 +71,22 @@ print(await sequence.first())
 // 1
 ```
 
+#### Last
+
+```swift
+let sequence = AsyncStream<Int> { continuation in
+    continuation.yield(1)
+    continuation.yield(2)
+    continuation.yield(3)
+    continuation.finish()
+}
+
+print(await sequence.last())
+
+// Prints:
+// 3
+```
+
 #### Collect
 
 ```swift