thornpig

//copied from Ben Dodson's website.
class ViewController: UIViewController {

    @IBOutlet weak var label: UILabel!
    
    override func viewDidLoad() {
        super.viewDidLoad()
        NotificationCenter.default.addObserver(self, selector: #selector(updateUI), name: .UIContentSizeCategoryDidChange, object: nil)
        updateUI()
    }

thornpig

scrollView.directionalLockEnabled still allows diagonal scrolling.
-(void)scrollViewWillBeginDragging:(UIScrollView *)scrollView
{
    self.initialOffeset = scrollView.contentOffset;
}

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    //lock scroll direction
    CGFloat xdis = scrollView.contentOffset.x - self.initialOffeset.x;

thornpig

//need double animation blocks
if (self.tableView.contentInset.top == 0)
{
    UIEdgeInsets tableViewInset = self.tableView.contentInset;
    tableViewInset.top = -1.*kTableHeaderHeight;
    [UIView animateWithDuration: 0 animations: ^(void){} completion:^(BOOL finished) {
        [UIView animateWithDuration: 0.5 animations:^{
        //no need to set contentOffset, setting contentInset will change contentOffset accordingly.
            self.tableView.contentInset = tableViewInset;  
        }];

thornpig

The cause of this problem is when the contentInset is set, contentOffset is also set to a value according to the new value of contentInset. 
So restore contentOffset to its old value after setting contentInset solves the problem. 
It seems the animation block is not needed in my app with iOS 9.0.

- (void)setLoadingScrollViewInsets:(UIScrollView *)scrollView
{
    UIEdgeInsets loadingInset = scrollView.contentInset;
    loadingInset.top += self.view.frame.size.height;

    CGPoint contentOffset = scrollView.contentOffset;

thornpig

//The main queue must be associated with the main thread.
//The main thread is not exclusively associated with the main queue.
//For example, when disptach_sync is used to dispatch a task from queue A to queue B, 
//queue B will use the same thread queue A is using to execute the task. 
//So, if a task is dispatched to a non-main queue from the main queue with dispatch_sync,  
//the non-main queue will use the main thread to execute the task.

//Check if a task is running on the main thread,
[NSThread isMianThread];

thornpig

//with semaphore
self.sem = disptach_semaphore_create(0);
[someAsyncTask start]; //someAsyncTask needs to call dispatch_semaphore_signal(self.sem) after the its work is done.
disptach_semaphore_wait(self.sem, DISPATCH_TIME_FOREVER);
NSLog(@"task is done!");

//with NSRunloop
self.taskIsDone = NO;
[someAsyncTask start]; //someAsyncTask needs to set self.taskIsDone = YES after the work is done.
while (!self.taskIsDone)

thornpig

To be able to import non-native framework files in Xctest, 
go to test target configuration -> build settings -> frame work search path,
add $(PROJECT_DIR) entry.

thornpig

Make sure Product->Scheme->Edit Scheme->Run is using "Debug" mode

(lldb) p NSPointFromString(@"{10.0, 20.0}");
error: 'NSPointFromString' has unknown return type; cast the call to its declared return type
error: 1 errors parsing expression
(lldb) p (NSPoint)NSPointFromString(@"{10.0, 20.0}”);
(NSPoint) $0 = (x = 10, y = 20)
(lldb) e @import UIKit
(lldb) po self.view.bounds

thornpig

ssh to node server
sudo apt-get update
sudo apt-get install git nodejs npm supervisor

ssh to mongodb server
sudo vi /etc/mongod.conf
change binip to 0.0.0.0

on dev terminal
gcloud compute firewall-rules create default-allow-mongo \

thornpig

Suppose we have a presenting vc, vca,  and a presented vc, vcb
If vca presentes vcb with UIModalPresentationFullScreen style, 
vca's view will be moved to
transitionContext's containerView. During the transition animation 
vcb's view is added on top of vca's view to the containerView. After the trainsition completes vca's view
is removed from the containerView, and vca has disappeared. During the dismissing trainsion, vca's view has to be
inserted to the containerView beneath vcb's view, so that vca's view will be revealed
as vcb's view moves off screen. If vca's view is not inserted back to containerView, a
black screen will be displayed at the end of the transition before vca's view appears.