Use a weak-memory NSHashTable for referencing iterators in HTML Document

This breaks the retain cycle between the document and the attached node
iterator.

Fixes #4

Sources/HTMLDocument.m

@@ -20,8 +20,8 @@
 @interface HTMLDocument ()
 {
 	HTMLDocument *_inertTemplateDocument;
-	NSMutableArray *_nodeIterators;
 	NSMutableArray *_ranges;
+	NSHashTable *_nodeIterators;
 }
 @property (nonatomic, assign) HTMLDocumentReadyState readyState;
 @end
@@ -41,8 +41,8 @@
 	self = [super initWithName:@"#document" type:HTMLNodeDocument];
 	if (self) {
 		_readyState = HTMLDocumentLoading;
-		_nodeIterators = [NSMutableArray new];
 		_ranges = [NSMutableArray new];
+		_nodeIterators = [[NSHashTable alloc] initWithOptions:NSHashTableWeakMemory capacity:10];
 	}
 	return self;
 }

Tests/HTMLKitTestUtil.h

@@ -11,5 +11,6 @@
 @interface HTMLKitTestUtil : NSObject
 
 + (NSInvocation *)addTestToClass:(Class)cls withName:(NSString *)name block:(id)block;
++ (id)ivarForInstacne:(id)instance name:(NSString *)name;
 
 @end

Tests/HTMLKitTestUtil.m

@@ -26,4 +26,10 @@
 	return invocation;
 }
 
++ (id)ivarForInstacne:(id)instance name:(NSString *)name
+{
+	Ivar ivar = class_getInstanceVariable([instance class], [name UTF8String]);
+	return object_getIvar(instance, ivar);
+}
+
 @end

Tests/HTMLNodeIteratorTests.m

@@ -8,6 +8,7 @@
 
 #import <XCTest/XCTest.h>
 #import "HTMLDOM.h"
+#import "HTMLKitTestUtil.h"
 
 @interface HTMLKitNodeIteratorTests : XCTestCase
 
@@ -565,4 +566,30 @@ static HTMLNode * (^ LastDescendant)(HTMLNode *) = ^ HTMLNode * (HTMLNode *node)
 	XCTAssertEqual(iterator.pointerBeforeReferenceNode, NO);
 }
 
+#pragma mark - Bug Fixes
+
+- (void)testBugFix_Issue_4
+{
+	HTMLDocument *document = [HTMLDocument documentWithString:@"<ul><li>1<li>2"];
+
+	NSHashTable *nodeIterators = [HTMLKitTestUtil ivarForInstacne:document name:@"_nodeIterators"];
+	XCTAssertTrue([nodeIterators isKindOfClass:[NSHashTable class]]);
+
+	// document.body uses an iterator internally
+	HTMLElement *body =	document.body;
+	XCTAssertNotNil(body);
+
+	// iterator should be deallocated and detached at this point
+	XCTAssertEqual(0, nodeIterators.count);
+
+	// iterator should be autoreleased, deallocated and detached after autoreleasepool
+	@autoreleasepool {
+		HTMLNodeIterator *iterator = [[HTMLNodeIterator alloc] initWithNode:body];
+		[iterator nextNode];
+		XCTAssertEqual(1, nodeIterators.count);
+	}
+
+	XCTAssertEqual(0, nodeIterators.count);
+}
+
 @end