cocoa-touch - w3toppers.com

How to automatically size UIScrollView to fit the content

The best method I’ve ever come across to update the content size of a UIScrollView based on its contained subviews: Objective-C CGRect contentRect = CGRectZero; for (UIView *view in self.scrollView.subviews) { contentRect = CGRectUnion(contentRect, view.frame); } self.scrollView.contentSize = contentRect.size; Swift let contentRect: CGRect = scrollView.subviews.reduce(into: .zero) { rect, view in rect = rect.union(view.frame) } scrollView.contentSize … Read more

What’s the difference between [NSNull null] and nil?

Directly from Apple: The NSNull class defines a singleton object you use to represent null values in situations where nil is prohibited as a value (typically in a collection object such as an array or a dictionary). So in your example, that’s exactly what’s happening, the programmer is choosing to put a null object into … Read more

Programmatically opening the settings app (iPhone) [duplicate]

As of iOS 5.0 you are able to open the settings app using the “prefs://” URL scheme. You are out of luck on earlier versions.

Generate hash from UIImage

I wound up using the following code to accomplish the task. Note that this requires that you import <CommonCrypto/CommonDigest.h>: unsigned char result[CC_MD5_DIGEST_LENGTH]; NSData *imageData = [NSData dataWithData:UIImagePNGRepresentation(inImage)]; CC_MD5([imageData bytes], [imageData length], result); NSString *imageHash = [NSString stringWithFormat: @”%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X”, result[0], result[1], result[2], result[3], result[4], result[5], result[6], result[7], result[8], result[9], result[10], result[11], result[12], result[13], result[14], result[15] ];

applicationWillTerminate: not being called

From Apple docs: For applications that do not support background execution or are linked against iOS 3.x or earlier, this method is always called when the user quits the application. For applications that support background execution, this method is generally not called when the user quits the application because the application simply moves to the … Read more

How can I detect whether the iphone has been rebooted since last time app started

This seems like it would work: get the time since last reboot, and for this example, let’s store it in a variable called ‘tslr’ (duration in milliseconds I guess, BTW, how do you get that?) get the current time, store it in variable ‘ct’ for example compute the last reboot time (let’s call it ‘lr’), … Read more

UIColor colorWithRed:green:blue:alpha: always returns white unless one argument is 0

The parameter aren’t a values of 0 to 255 but a float between 0.0 and 1.0: [UIColor colorWithRed:0.0f/255.0f green:155.0f/255.0f blue:218.0f/255.0f alpha:1.0f];

Detecting if UIView is intersecting other UIViews

There’s a function called CGRectIntersectsRect which receives two CGRects as arguments and returns if the two given rects do intersect. And UIView has subviews property which is an NSArray of UIView objects. So you can write a method with BOOL return value that’ll iterate through this array and check if two rectangles intersect, like such: … Read more

UIControlEventTouchDragExit triggers when 100 pixels away from UIButton

Override continueTrackingWithTouch:withEvent: like this to send DragExit/DragOutside events inside of the default gutter: – (BOOL)continueTrackingWithTouch:(UITouch *)touch withEvent:(UIEvent *)event { CGFloat boundsExtension = 25.0f; CGRect outerBounds = CGRectInset(self.bounds, -1 * boundsExtension, -1 * boundsExtension); BOOL touchOutside = !CGRectContainsPoint(outerBounds, [touch locationInView:self]); if(touchOutside) { BOOL previousTouchInside = CGRectContainsPoint(outerBounds, [touch previousLocationInView:self]); if(previousTouchInside) { NSLog(@”Sending UIControlEventTouchDragExit”); [self sendActionsForControlEvents:UIControlEventTouchDragExit]; } else … Read more

Looping using NSRange

It kind of sounds like you’re expecting NSRange to be like a Python range object. It’s not; NSRange is simply a struct typedef struct _NSRange { NSUInteger location; NSUInteger length; } NSRange; not an object. Once you’ve created one, you can use its members in a plain old for loop: NSUInteger year; for(year = years.location; … Read more