n-b/TestAttributedStrings.m

## TestAttributedStrings.m

@import UIKit;


#pragma mark - Main View Controller

@interface ViewController : UITableViewController
@end


@implementation ViewController
// A simple TableViewController with a large number of cell
//
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return 10000; }


// A small HTML fragment is parsed and set as the attributed title for each cell
//
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    UITableViewCell * cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
    NSString * htmlSource = [NSString stringWithFormat:@"<html><p>Row <i>%@</i></p></html>", @(indexPath.row)];
    NSAttributedString * attributedText = [[NSAttributedString alloc] initWithData:[htmlSource dataUsingEncoding:NSUTF8StringEncoding]
                                                                           options:@{NSDocumentTypeDocumentAttribute:NSHTMLTextDocumentType}
                                                                documentAttributes:nil
                                                                             error:nil];
    cell.textLabel.attributedText = attributedText;
    return cell;
}


- (void) scrollViewDidScroll:(UIScrollView *)scrollView
{
    for (NSIndexPath * indexPath in [self.tableView indexPathsForVisibleRows]) {
        [self.tableView cellForRowAtIndexPath:indexPath]; // CRASH
        // This crashes as soon as you start scrolling.
        //
        // [self.tableView visibleCells] doesn't match [self.tableView indexPathsForVisibleRows]
        // (There are less cells than there are visible rows.)
        //
        // This happens because HTML parsing uses Webkit in the main thread, which requires running the main runloop in a common mode.
        //
        // In other words, -scrollViewDidScroll is called inside -cellForRowAtIndexPath.
    }
}

@end


#pragma mark - App Setup

@interface AppDelegate : UIResponder <UIApplicationDelegate>
@property (strong, nonatomic) UIWindow *window;
@end

@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    self.window.rootViewController = [ViewController new];
    [self.window makeKeyAndVisible];
    return YES;
}
@end

int main(int argc, char * argv[])
{
    @autoreleasepool {
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
    }
}

	@import UIKit;


	#pragma mark - Main View Controller

	@interface ViewController : UITableViewController
	@end


	@implementation ViewController
	// A simple TableViewController with a large number of cell
	//
	- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return 10000; }


	// A small HTML fragment is parsed and set as the attributed title for each cell
	//
	- (UITableViewCell )tableView:(UITableView )tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
	{
	UITableViewCell * cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:nil];
	NSString * htmlSource = [NSString stringWithFormat:@"<html><p>Row <i>%@</i></p></html>", @(indexPath.row)];
	NSAttributedString * attributedText = [[NSAttributedString alloc] initWithData:[htmlSource dataUsingEncoding:NSUTF8StringEncoding]
	options:@{NSDocumentTypeDocumentAttribute:NSHTMLTextDocumentType}
	documentAttributes:nil
	error:nil];
	cell.textLabel.attributedText = attributedText;
	return cell;
	}


	- (void) scrollViewDidScroll:(UIScrollView *)scrollView
	{
	for (NSIndexPath * indexPath in [self.tableView indexPathsForVisibleRows]) {
	[self.tableView cellForRowAtIndexPath:indexPath]; // CRASH
	// This crashes as soon as you start scrolling.
	//
	// [self.tableView visibleCells] doesn't match [self.tableView indexPathsForVisibleRows]
	// (There are less cells than there are visible rows.)
	//
	// This happens because HTML parsing uses Webkit in the main thread, which requires running the main runloop in a common mode.
	//
	// In other words, -scrollViewDidScroll is called inside -cellForRowAtIndexPath.
	}
	}

	@end








	#pragma mark - App Setup

	@interface AppDelegate : UIResponder <UIApplicationDelegate>
	@property (strong, nonatomic) UIWindow *window;
	@end

	@implementation AppDelegate
	- (BOOL)application:(UIApplication )application didFinishLaunchingWithOptions:(NSDictionary )launchOptions
	{
	self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
	self.window.rootViewController = [ViewController new];
	[self.window makeKeyAndVisible];
	return YES;
	}
	@end

	int main(int argc, char * argv[])
	{
	@autoreleasepool {
	return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
	}
	}