Merge pull request #75 from MindSea/fix-simultaneous-access

Fix "modification requires exclusive access" crash when building with…

Author: Sergey D

PullToRefresh/PullToRefresh.swift

@@ -90,14 +90,14 @@ open class PullToRefresh: NSObject {
 
     // MARK: KVO
 
-    fileprivate var KVOContext = "PullToRefreshKVOContext"
+    fileprivate static var KVOContext = "PullToRefreshKVOContext"
     fileprivate let contentOffsetKeyPath = "contentOffset"
     fileprivate let contentInsetKeyPath = "contentInset"
     fileprivate let contentSizeKeyPath = "contentSize"
     fileprivate var previousScrollViewOffset: CGPoint = CGPoint.zero
 
     override open func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
-        if (context == &KVOContext && keyPath == contentOffsetKeyPath && object as? UIScrollView == scrollView) {
+        if (context == &PullToRefresh.KVOContext && keyPath == contentOffsetKeyPath && object as? UIScrollView == scrollView) {
             var offset: CGFloat
             switch position {
             case .top:
@@ -125,11 +125,11 @@ open class PullToRefresh: NSObject {
                 }
             default: break
             }
-        } else if (context == &KVOContext && keyPath == contentSizeKeyPath && object as? UIScrollView == scrollView) {
+        } else if (context == &PullToRefresh.KVOContext && keyPath == contentSizeKeyPath && object as? UIScrollView == scrollView) {
             if case .bottom = position {
                 refreshView.frame = CGRect(x: 0, y: scrollView!.contentSize.height, width: scrollView!.bounds.width, height: refreshView.bounds.height)
             }
-        } else if (context == &KVOContext && keyPath == contentInsetKeyPath && object as? UIScrollView == scrollView) {
+        } else if (context == &PullToRefresh.KVOContext && keyPath == contentInsetKeyPath && object as? UIScrollView == scrollView) {
             if self.state == .initial {
                 scrollViewDefaultInsets = scrollView!.contentInset
             }
@@ -146,9 +146,9 @@ open class PullToRefresh: NSObject {
             return
         }
 
-        scrollView.addObserver(self, forKeyPath: contentOffsetKeyPath, options: .initial, context: &KVOContext)
-        scrollView.addObserver(self, forKeyPath: contentSizeKeyPath, options: .initial, context: &KVOContext)
-        scrollView.addObserver(self, forKeyPath: contentInsetKeyPath, options: .new, context: &KVOContext)
+        scrollView.addObserver(self, forKeyPath: contentOffsetKeyPath, options: .initial, context: &PullToRefresh.KVOContext)
+        scrollView.addObserver(self, forKeyPath: contentSizeKeyPath, options: .initial, context: &PullToRefresh.KVOContext)
+        scrollView.addObserver(self, forKeyPath: contentInsetKeyPath, options: .new, context: &PullToRefresh.KVOContext)
 
         isObserving = true
     }
@@ -158,9 +158,9 @@ open class PullToRefresh: NSObject {
             return
         }
 
-        scrollView.removeObserver(self, forKeyPath: contentOffsetKeyPath, context: &KVOContext)
-        scrollView.removeObserver(self, forKeyPath: contentSizeKeyPath, context: &KVOContext)
-        scrollView.removeObserver(self, forKeyPath: contentInsetKeyPath, context: &KVOContext)
+        scrollView.removeObserver(self, forKeyPath: contentOffsetKeyPath, context: &PullToRefresh.KVOContext)
+        scrollView.removeObserver(self, forKeyPath: contentSizeKeyPath, context: &PullToRefresh.KVOContext)
+        scrollView.removeObserver(self, forKeyPath: contentInsetKeyPath, context: &PullToRefresh.KVOContext)
 
         isObserving = false
     }