If your object is myObject, and you want to test to see if it is an NSString, the code would be: [myObject isKindOfClass:[NSString class]] Likewise, if you wanted to test myObject for a UIImageView: [myObject isKindOfClass:[UIImageView class]]
Use an NSNumberFormatter: NSNumberFormatter *f = [[NSNumberFormatter alloc] init]; f.numberStyle = NSNumberFormatterDecimalStyle; NSNumber *myNumber = [f numberFromString:@”42″]; If the string is not a valid number, then myNumber will be nil. If it is a valid number, then you now have all of the NSNumber goodness to figure out what kind of number it actually is.
I use dispatch_after so often that I wrote a top-level utility function to make the syntax simpler: func delay(delay:Double, closure:()->()) { dispatch_after( dispatch_time( DISPATCH_TIME_NOW, Int64(delay * Double(NSEC_PER_SEC)) ), dispatch_get_main_queue(), closure) } And now you can talk like this: delay(0.4) { // do stuff } Wow, a language where you can improve the language. What could … Read more
I ended up solving my own problem. Apparently in iOS 8 SDK, requestAlwaysAuthorization (for background location) or requestWhenInUseAuthorization (location only when foreground) call on CLLocationManager is needed before starting location updates. There also needs to be NSLocationAlwaysUsageDescription or NSLocationWhenInUseUsageDescription key in Info.plist with a message to be displayed in the prompt. Adding these solved my … Read more
From proper way to do uitextfield text change call back: I catch the characters sent to a UITextField control something like this: // Add a “textFieldDidChange” notification method to the text field control. In Objective-C: [textField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged]; In Swift: textField.addTarget(self, action: #selector(textFieldDidChange), for: .editingChanged) Then in the textFieldDidChange method you can examine the … Read more
@implementation TestClass – (void) dealloc { // If you don’t remove yourself as an observer, the Notification Center // will continue to try and send notification objects to the deallocated // object. [[NSNotificationCenter defaultCenter] removeObserver:self]; [super dealloc]; } – (id) init { self = [super init]; if (!self) return nil; // Add this instance of … Read more
The original code for the Cocoa frameworks came from the NeXTSTEP libraries Foundation and AppKit (those names are still used by Apple’s Cocoa frameworks), and the NextStep engineers chose to prefix their symbols with NS. Because Objective-C is an extension of C and thus doesn’t have namespaces like in C++, symbols must be prefixed with … Read more
iOS 8.0 introduces the layoutMargins property on cells AND table views. This property isn’t available on iOS 7.0 so you need to make sure you check before assigning it! The easy fix is to subclass your cell and override the layout margins property as suggested by @user3570727. However you will lose any system behavior like … Read more
You can check if [string length] == 0. This will check if it’s a valid but empty string (@””) as well as if it’s nil, since calling length on nil will also return 0.
If you see this warning: warning: receiver ‘MyCoolClass’ is a forward class and corresponding @interface may not exist you need to #import the file, but you can do that in your implementation file (.m), and use the @class declaration in your header file. @class does not (usually) remove the need to #import files, it just … Read more