thornpig

NSUInteger a = 0;
NSInteger b = 3;
NSInteger c = 1;
BOOL d = c >= a - b; //d is NO because a - b is implicitly converted to NSUInteger 4294967294

NSString *string = @"";
BOOL e = c >=  string.length - b; // e is NO because string.lenth returns NSUInteger.

thornpig

self.newsFeedDescriptionLabel.font = nil; //without this line the font attribute may not apply to the label

thornpig

-(void)viewDidLayoutSubviews
{
    self.containerView.frame = self.view.bounds;
    self.currentVC.view.frame = self.containerView.bounds;
}

-(void)showChildViewController:(UIViewController *)childVC
{
    [self addChildViewController:childVC];
    self.containerView.frame = self.view.bounds;

thornpig

To set the back button title for a view controller without changing it's title you use:

Objective-C:

self.navigationItem.backBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:self.navigationItem.backBarButtonItem.style target:nil action:nil];
Swift:

navigationItem.backBarButtonItem = UIBarButtonItem(title: "", style: .Plain, target: nil, action: nil)
To be clear, this is done on the view controller that you would see if you hit the back button. 
i.e. instead of seeing '< Settings' you want to just see '<' then on your SettingsViewController you would put this in your init. 

thornpig

In UIViewController subclasses
-(void)viewDidLayoutSubviews
{
    self.containerView.frame = self.view.bounds;
    self.currentVC.view.frame = self.containerView.bounds;
}

In UIView subclasses
-(void)layoutSubviews
{

thornpig

-(void)layoutSubviews
{
    [super layoutSubviews];
    ....
}

thornpig

-(void)updateConstraints
{
    [super updateConstraints];
    if (self.binaryFiles.count > 0)
    {
        //deactivate first, then activate, then change constant
        [NSLayoutConstraint deactivateConstraints: @[self.attachmentButtonConstraintHeight]];
        [NSLayoutConstraint activateConstraints: @[self.attachmentButtonConstraintAspectRatio]];
//        self.attachmentButtonConstraintHeight.active = NO;
//        self.attachmentButtonConstraintAspectRatio.active = YES;

thornpig

CFDataRef imageData = (__bridge CFDataRef)[self getData];
CGImageSourceRef imageSourceRef = CGImageSourceCreateWithData(imageData, nil);
CFDictionaryRef options = (__bridge CFDictionaryRef) @{
                                                               (id) kCGImageSourceCreateThumbnailWithTransform : @YES,
                                                               (id) kCGImageSourceCreateThumbnailFromImageAlways : @YES,
                                                               (id) kCGImageSourceThumbnailMaxPixelSize : @(100)};
CGImageRef imageRef = CGImageSourceCreateThumbnailAtIndex(imageSourceRef, 0 , options);
thumbnail = [UIImage imageWithCGImage: imageRef];
return thumbnail;

thornpig

id imageSource = cell.imageSource;
dispatch_async(queue, ^{
   //block captures imageSource
   UIImage *thumbNail = getImageFromSource(imageSource);
  dispatch_sync(dispatch_get_main_queue(), ^{
  //block captures cell
  //if imageSource does not match cell.imageSource, it means the cell is resued before the background thread returns the image, 
  // and the image requested for the already invisible cell may be returned after the current cell obtains its image, in which case
  // the returned image should not be used.
  if ([imagaeSource isEqualToArray: cell.imageSource])

thornpig

－(void)viewWillAppear:(BOOL)animated
{
 //force the layout before the drawing cycle begins, so that when the tableview setup its cells the subviews of the cell 
 already have the frame information of the cell. For example, with this line, the text view inside the cell can use 
 the cell width to calculate depth to accormodate its text.
    [self.view layoutIfNeeded];
    [self.tableView reloadData];
}