ImageDownloader can now enqueue multiple image downloads at once.

Source/ImageDownloader.swift

@@ -399,6 +399,37 @@ public class ImageDownloader {
         return nil
     }
 
+    /**
+        Creates a download request using the internal Alamofire `Manager` instance for each specified URL request.
+
+        For each request, if the same download request is already in the queue or currently being downloaded, the
+        filter and completion handler are appended to the already existing request. Once the request completes, all
+        filters and completion handlers attached to the request are executed in the order they were added.
+        Additionally, any filters attached to the request with the same identifiers are only executed once. The
+        resulting image is then passed into each completion handler paired with the filter.
+
+        You should not attempt to directly cancel any of the `request`s inside the request receipts array since other
+        callers may be relying on the completion of that request. Instead, you should call
+        `cancelRequestForRequestReceipt` with the returned request receipt to allow the `ImageDownloader` to optimize
+        the cancellation on behalf of all active callers.
+
+        - parameter URLRequests: The URL requests.
+        - parameter filter       The image filter to apply to the image after each download is complete.
+        - parameter completion:  The closure called when each download request is complete.
+
+        - returns: The request receipts for the download requests if available. If an image is stored in the image
+                   cache and the URL request cache policy allows the cache to be used, a receipt will not be returned
+                   for that request.
+    */
+    public func downloadImages(
+        URLRequests URLRequests: [URLRequestConvertible],
+        filter: ImageFilter? = nil,
+        completion: CompletionHandler? = nil)
+        -> [RequestReceipt]
+    {
+        return URLRequests.flatMap { downloadImage(URLRequest: $0, filter: filter, completion: completion) }
+    }
+
     /**
         Cancels the request in the receipt by removing the response handler and cancelling the request if necessary.
 

Tests/ImageDownloaderTests.swift

@@ -176,6 +176,37 @@ class ImageDownloaderTestCase: BaseTestCase {
         XCTAssertTrue(result2?.isSuccess ?? false, "result 2 should be a success case")
     }
 
+    func testThatItCanEnqueueMultipleImages() {
+        // Given
+        let downloader = ImageDownloader()
+
+        let download1 = URLRequest(.GET, "https://httpbin.org/image/jpeg")
+        let download2 = URLRequest(.GET, "https://httpbin.org/image/png")
+
+        let expectation = expectationWithDescription("both downloads should succeed")
+        var completedDownloads = 0
+
+        var results: [Result<Image, NSError>] = []
+
+        // When
+        downloader.downloadImages(URLRequests: [download1, download2], filter: nil) { closureResponse in
+            results.append(closureResponse.result)
+
+            ++completedDownloads
+            if completedDownloads == 2 { expectation.fulfill() }
+        }
+
+        let activeRequestCount = downloader.activeRequestCount
+
+        waitForExpectationsWithTimeout(timeout, handler: nil)
+
+        // Then
+        XCTAssertEqual(activeRequestCount, 2, "active request count should be 2")
+
+        XCTAssertTrue(results[0].isSuccess, "the first result should be a success case")
+        XCTAssertTrue(results[1].isSuccess, "the second result should be a success case")
+    }
+
     func testThatItDoesNotExceedTheMaximumActiveDownloadsLimit() {
         // Given
         let downloader = ImageDownloader(maximumActiveDownloads: 1)