From 250f92970ae458cb4ece73b85c18e26044a123c0 Mon Sep 17 00:00:00 2001
From: Sam Stigler <sstigler@phunware.com>
Date: Sun, 9 Oct 2016 17:19:12 -0500
Subject: [PATCH 1/2] Works around crash seen when using layout with
 AsyncDisplayKit.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

AsyncDisplayKit was requesting a layout before the collection view had items (or sections). That led to a crash because the `numberOfItems` computed property was querying the collection view for the number of items in non-existent section 0. This fix updates the `numberOfItems` computed property to always return 0 if there aren’t any sections in the collection view.
---
 Source/SFFocusViewLayout.swift | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Source/SFFocusViewLayout.swift b/Source/SFFocusViewLayout.swift
index d5f59dc..a223360 100644
--- a/Source/SFFocusViewLayout.swift
+++ b/Source/SFFocusViewLayout.swift
@@ -126,6 +126,10 @@ public class SFFocusViewLayout: UICollectionViewLayout {
 private extension UICollectionViewLayout {
 
     var numberOfItems: Int {
+        guard collectionView?.numberOfSections() > 0 else {
+            return 0
+        }
+        
         return collectionView!.numberOfItemsInSection(0)
     }
 

From cff2cfd8433eed9537001c9be14c07a606ec9b9e Mon Sep 17 00:00:00 2001
From: Sam Stigler <sstigler@phunware.com>
Date: Sun, 9 Oct 2016 17:25:14 -0500
Subject: [PATCH 2/2] Adds test for zero-sections fix.

---
 Tests/CollectionViewController.swift | 4 +++-
 Tests/Tests.swift                    | 5 +++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Tests/CollectionViewController.swift b/Tests/CollectionViewController.swift
index f3a093e..ae6100a 100644
--- a/Tests/CollectionViewController.swift
+++ b/Tests/CollectionViewController.swift
@@ -13,6 +13,8 @@ private let reuseIdentifier = "Cell"
 class CollectionViewController: UICollectionViewController {
 
     var items = [Int]()
+    
+    var numberOfSectionsToReturn = 1
 
     override func viewDidLoad() {
         super.viewDidLoad()
@@ -23,7 +25,7 @@ class CollectionViewController: UICollectionViewController {
     // MARK: UICollectionViewDataSource
 
     override func numberOfSectionsInCollectionView(collectionView: UICollectionView) -> Int {
-        return 1
+        return numberOfSectionsToReturn
     }
 
 
diff --git a/Tests/Tests.swift b/Tests/Tests.swift
index 75a8a26..e8088c5 100644
--- a/Tests/Tests.swift
+++ b/Tests/Tests.swift
@@ -81,5 +81,10 @@ class Tests: XCTestCase {
     func testLayoutShouldInvalidateLayoutForBoundsChange() {
         XCTAssertTrue(focusViewLayout.shouldInvalidateLayoutForBoundsChange(CGRect()))
     }
+    
+    func testCanPrepareLayoutForCollectionViewWithZeroSections() {
+        collectionViewController?.numberOfSectionsToReturn = 0
+        focusViewLayout.prepareLayout()
+    }
 
 }